I just did.
a 1024x768 wallpaper which turned out pretty well I think, but... I'm really quite nervous about people's reactions to it. (it's a screened contest right now so I can't share it with y'all). The text is... not right, the fonts work I think, but part of the challenge was to include specific words and they just ended up not quite fitting with the image. That said, I do currently have it as my desktop background so I clearly don't hate it that much.... :)
Ah well, we'll see.
ETA Voting is open - yup, the wallpaper I made is in there. You don't have to be a community member to vote by the way, so y'know, if you see anything you like... :) (It's a Doctor Who community and there are a couple of walls in there using graphics from the final episode of season two)