Post links to your best computer or programming wallpapers!
A Good wallpaper for windows is "None" with desktop icons hidden... its faster and elegant..
My favorite Windows wallpaper is actually a practical joke: when your coworker leaves his computer unguarded, hit PrintScreen to copy his entire desktop, then paste it into Paint and save it somewhere. Move all of his desktop icons to a folder somewhere (or just delete them if you don't like him very much), move the taskbar off the screen, and then make the bitmap you just saved into his wallpaper.
When he comes back, his desktop will look just the same as it did before, but he won't be able to click on anything. Great fun!
Personally I like high resolution space related images; either real images from the Hubble Telescope (or similar) or artist impressions of star explosions, galaxies etc.
I have enough trouble getting distracted as it is, so usually I pick something plain or some abstract art.