Before introducing the cards I've made, let me first tell you how I made these. I used Inkscape to make the drawings. As you can see in the picture above, there are two types of card: door cards (left) and treasure cards (right). The cards are a 55 × 87 mm rectangle with rounded edges and the inside of the border is 50 × 82 mm. Next, the colors. The border color (as well as the color for the outlines of the drawings and the text) is #270b00 (=R:39 G:11 B:0). The background color of the door cards is #e7daa7 (=R:231 G:218 B:167). And the background color of the treasure cards is a pattern, but #ffc654 (=R:255 G:198 B:84) is close enough.
Next, the fonts. The font I used for the title of each card (and the title on the box) is called Quasimodo. The font I used for the rest of the text on the card is called Caslon Antique. Font sizes are as follows: for card titles, 16 pt.; for monster levels/bonus points and the words "bad stuff", 12 pt.; for descriptions (including the descriptions of the "bad stuff"), usable by, and text at the bottom of the card (race/treasure/class/level/steed//big/hands/gold pieces), 11 pt. The beginning of normal text paragraphs on the card are indented 3 spaces. Normal text paragraphs are left justified. The text at the bottom of the card is bolded. The words "bad stuff" are both italicized and bolded. I also added a little icon at the bottom to indicate that these are part of the "Crooked Cards" Expansion Pack.
When drawing monsters or other characters for these cards in Inkscape, make your lines 2 pixels wide. Fill colors that are available to you are, from left to right: #270b00 (=R:39 G:11 B:0); #46361d (=R:70 G:54 B:29); #5f5025 (=R:95 G:80 B:37); #7e7346 (=R:126 G:115 B:70); #9f9574 (=R:159 G:149 B:116); #c0b8a1 (=R:192 G:184 B:161); and, of course, white (#ffffff; =R:255 G:255 B:255).
And now to introduce you to my custom door cards:
First up is a door card featuring a monster: the Abominable Snow Monster from the classic Windows game SkiFree. When you venture too far outside of the map (either up or down) this creature rushes out and devours you. You can try to get away, but he inevitably catches you. (If you evade him for long enough, though, a second shows up.) After he's done eating you, he celebrates. Now you finally have a chance to beat him. But he's a tough bugger, so if you lose the "bad stuff" is bad.
Next up we have a door card featuring a monster: a conjoined chicken. One of the baby books Lillian has features a picture of two chicks. They are so close together that it looks like one chick with two heads and four legs. So I traced it and made it into a Munchkin monster. I modeled the characteristics of the card after the Large Angry Chicken, but doubled everything.
This one is a door card that's laden with superb prose, careful and believable characterization, and a meticulous and intricate plot: Sparkly Vampire Eyebrows. Yeah… This is a not-very-subtle reference to the Twilight series  and to the fact that Robert Pattinson (a.k.a. Edward) seems to do most of his acting with his unusually bushy eyebrows. The reasoning behind the bonus against female players should be self-evident. The bonus against elves is because that's how the Munchkin creators treat that race—as though they're effeminate. The "bad stuff" alludes to a couple of the worst lines from the movie (and presumably from the book).
This card, like the previous one, takes a jab at the Twilight series. This time it's making fun of the fact that the character of Jacob Black (who is a werewolf) spends most of his time in the second and third movies  with nothing on but a pair of cutoffs—even when it's snowing. Hence barewolf.
This one is pretty self-explanatory. Ew.
The main thing I remember about the 1971 film Willy Wonka & the Chocolate Factory is how much I hate the Oompa Loompas. They look freaky, they show up all the time, and their song is so obnoxious. Gah! So the bad stuff is calculated to reflect that. At least I don't make you sing their song! Their name is similar to the Goomba, the ubiquitous enemy creature in Super Mario Bros. that resembles a shiitake mushroom. I replaced the Oompa Loompa's heads with Goombas. I really wanted them to still have the weird green hair of the Oompa Loompas, but everything I tried just looked funny.
There are lots of mystery shows (including mystery comedies, like The Pink Panther series and Private Eyes) which have paintings with eyes. Or, more properly, the house everyone is staying in has an old painting with a secret passageway behind it. At some point someone is shown peaking out of the painting. We know it's a person because their eyes move around. A lot. It's supposed to be scary, but I doubt that it is—unless you have ommetaphobia.
Another card that requires no explanation.
I can recall seeing commercials for an after-school animated series called Attack of the Killer Tomatoes. I never watched it, but I can still remember at least part of the theme song from the commercials.
Another bad one for emmetaphobes. This one refers to the statement often seen in text messages, IMs, chat rooms, etc.: "rolling eye(ball)s". This phrase is often used to suggest mild annoyance or to imply that you find whatever the other person just said or did to be corny or cheesy. To make things interesting, I make you roll the dice to figure out how many eyeballs you must fight. So even though the card says they're Level 1, by rolling three dice (or if you don't have three, role one die three times), you're effectively facing monsters that are anywhere from Level 3 to 18. When you read the bad stuff, I imagine you'll roll your eyes. Mission accomplished. One minor inconsistency, though. I couldn't find a good way to represent rolling eyeballs, so I made them bounce.
You're probably familiar with the nursery rhyme "The Eensey Weensey Spider" (or some variation thereof, like "The Itsy Bitsy Spider"). Well, despite it's diminutive size, it's actually quite deadly. So Little Miss Muffet was right to run away. It's diminished power against Halflings is in reference to the confrontation between Frodo and Shelob at the end of The Two Towers (the book, not the movie).
No one has ever actually seen this monster, but at some point in our lives we've all known it was there. If you jump out of bed to run away, it's got you. And if you manage to elude him at the start, he has a compatriot hiding in the closet who's sure to catch you. So all you can do is hide under the covers and hope they leave you alone. But in Munchkin you must fight. Good luck.
I think most of you (if not all) can tell this is an allusion to the Fighting Trees in the film The Wizard of Oz (or the Book The Wonderful Wizard of Oz). They have an extra advantage against Halflings because the Halflings mistake them for Ents. They also have an advantage against wizards because of the tree that gave Schmendrick so much trouble in the animated film The Last Unicorn.
The title of this one refers to the film The Princess Bride. I say the film and not the book because in the film it's rather obvious that the R.O.U.S.s are men in rat suits. I made this a picture a combination of Mickey Mouse, Chuck E. Cheese, and Jerry Mouse. But just to make sure we all know what's really being talked about, here, I left a clue in the "Bad Stuff". I also made one in color.
I also thought about doing a card based on the movie SHE , but since I've never actually seen it, I had no idea what to draw on the card, nor what type of card to make it, nor what conditions to set on it. It just seems like it would make a good card. So that will just have to go out as a suggestion for someone else to make.
See Custom Munchkin Treasure Cards I designed, here.
 See http://en.wikipedia.org/wiki/Munchkin (role-playing games).
 See my post Lillian's First Christmas.
 There are also some custom Munchkin cards I've found on the internet that I like: It's My Turn (on the right), The Old Sherwood Shuffle (bottom, center), Lose an Arm (bottom, right), Necklace of Shrunken Heads, Random Encounter, Holy Hand Grenade (top), Poser (but it shouldn't be worth any gold pieces since it's a door card), Monster Bodyguard, Cool-Looking Curvy Dagger, Inflation, It's So Fluffy I'm Gonna Die, Littlefoot, Unnatural Deed, and Peanut Butter and Orc Guts Spreader. goodbunny2000 over at deviantART has some good cards, but he also has some naughty cards so I can't link to any of them. Proceed at your own discretion. You can also get official Munchkin level counters here. You can the rules for Epic Munchkin for free here. You can learn about (and purchase) Munchkin Silver Pieces here. You can watch a demo of how to play Munchkin here.
 If you're unsure what Inkscape is, see my post Raster Graphics and Vector Graphics.
 That's approximately 2 3/16 × 3 7/16 inches or 194.882 × 308.268 pixels for the outside border and approximately 1 15/16 × 3 3/16 inches or 177.165 × 290.551 pixels for the inside border. I chose metric over standard measurement so I wouldn't have to convert the sixteenths of inches to decimals.
 You can download it here. This appears to be exactly the same font.
 You can download it here. This is really close, but isn't quite the right font: the fs look different.
 Learn more here (where you can also download the game for free).
 I briefly considered giving it one more head and making it a Turducken, but decided that that would be too busy.
 Read my review of the RiffTrax treatment of Twilight here.
 Perhaps that's a veiled commentary about the type of role player who chooses to be an elf?
 Read my reviews (with RiffTrax) here and here.
 See http://www.youtube.com/watch?v=qtURoWuzfpE.
 See http://en.wikipedia.org/wiki/She (film).
The images contained herein are my own creations. However, they are based on materials produced by Steve Jackson Games which are Copyright © 2012 by Steve Jackson Games. All Rights Reserved. My derivative works are not intended as copyright violations in any way. They are simply suggestions for cards that can be used to supplement the Munchkin card game. By themselves they are insufficient and require the purchase of the original Munchkin game (which I encourage you to do). All other copyrighted materials referenced in this post are used in a parodic manner and thus do not constitute a violation of the rights of the respective copyright holders.