Front
My QSL card uses Buckminster Fuller's Dymaxion map, to which I added a red dot at my QTH. This projection is the most accurate, but you do lose the feel for spherical relationships. Or at least I do! However, it's the only projection that preserves sizes and doesn't chop up any land masses. The image is a mosaic of actual satellite photography on days without clouds.
I use the picture to emphasize that there are no borders on earth. We're all here together.
The back of the card is a grayscale image of a bunch of slide rules. Yes, I enjoy using and collecting these neat old gadgets. :-) Let me know if you have any to get rid of!
To make the card, I used gimp and created the images at 300 dpi. (The above are scaled and compressed versions.) The Fists logo was taken from the logo at fists.org. You'll find a pointer to my logo XCF file on my main ham page under the Fists key. My Fists number is just a layer that you can turn off, so feel free to grab the file and modify it if you're a gimp user.