Here are my previous attempts in Woot.com's shirt design contest (derby).

Chip And A Chair

Derby # 73: Optimism
20th place

"Target Audience" inspired by the "For Dummies" book series

Derby # 72: Book Titles Re-Interpreted

6th place

The Flea Has Cats Again

Derby #69: Miniature Worlds

16th place

Picasso's The Old Guitar Hero

Derby #67: Video Games Through Art History

29th place

Scare Bears vs Unicorn

Derby #66: Versus

103rd place