Concept art for a game proposal I worked on in 2003. This is my take on the theme of an evil Cheshire Cat. He's got a lovely smile, don't you think? Sweating a little...

I think I can now reveal (as many have guessed) that this is based on "The Looking Glass Wars" by Frank Beddor.

Update 24th March 2010: After following up on a case of partial plagiarism of my cat piece, I have since received an apology from the artist responsible for copying it.
I am happy to draw a line under this now. But the moral of the story is that selling art which is copied from/"inspired by" imagery you find online is inexcusable, and will get noticed eventually. If using reference material for your work, always investigate the original's origins/ownership/IP rights and seek any necessary permissions before going public with it!