A little strange, but he's just SO darn cute! I've had him a long time, so I don't really remember where I originally found him. However, the artist who signed it is "Chamba."
This rainbow theme is called "Vienna2" and it is a theme for Winstep. You have to have Winstep in order to use this theme. It has a ton of great features, and it's simply the best desktop organization tool I've found. If you're interested in it, visit winstep.net