A good wallpaper reflects our personality? Programmers usually use the same kind of geeky wallpapers (Matrix, Star Wars, Abstract Art) and we like to impress friend and co-workers.
I use the ones from:
http://www.digitalblasphemy.com
There are some free ones there but I subscribe to it.
I really enjoy Frank Chimero's posters. They are hardly typical and inspire people to think.
The Hubble Ultra Deep Field
Billions ... and Billions ... and Billions of galaxies.
I like grabbing a new batch from Smashing Magazine each month. They also have other non-calendar wallpaper and often have articles that point to cool wall paper. If you use the DownloadThemAll Firefox extension, each month, you can quickly download all the ones that match your resolution with the right filter.
I use Display Fusion Pro to span and rotate them across my monitors.
Cartoon, nerd, geek. Damn. I get a good chuckle every time I lay my sight on it.
Fractal backgrounds! From Mandelbrot to Julia, they're always fun for backgrounds and quite pleasing.
No contest, the BSOD screen saver http://technet.microsoft.com/en-ca/sysinternals/bb897558.aspx this is especially funny when installed as a goat on somebody else's machine :)
There are some good abstract ones at InterfaceLIFT.
Check this sites for Dual, Triple and Quad monitor backgrounds.
Actually, most of the time, my background is plain black, because that's the sort of guy I am, but I do love the endless supply of demotivational posters, such as the series at http://dribbleglass.com/misinspired/confidence.htm. There's a whole swag of 'em on the net takin' the piss out of those useless motivational ones.
Or check out all their stuff at http://dribbleglass.com/subpages/strange/pictures.htm.
Currently this picture of a Peacekeeper missile testing, because (a) I like blue, (b) I think the name of the missile is interesting, and (c) a general fascination with atomic weapons. (Note: I'm not fascinated with the destruction, just the science, history, and the shape and colors of explosions.) Fun fact: the Peacekeeper missile carried (up to) ten nuclear missiles, each at twenty times the power of the Hiroshima bomb. See also: a French nuclear test.
I've been using this one for some time.. Recommended to all procrastinators out there..
I've usually got a cool picture from the NASA image of the day gallery Click! :-)
DeviantArt.com wallpapers http://wallpaper.deviantart.com/
DeviantArt will be able to detect your screen size and automatically present to you wallpapers with the exact dimensions of your screen.
Flickr.com Wallpaper Pool http://www.flickr.com/groups/wallpapers/pool/
Hi, I use pictures from www.mandolux.com, because I need pictures for a dual screen configuration with a resolution of each 1920x1080 = 3840*1080
Here's my current ones, (1440x900) side by side thanks to DisplayFusion:
http://img3.imageshack.us/img3/1655/ferrarilaunch2009.jpg
http://img197.imageshack.us/img197/3126/redbullaunch2009.jpg
More Formula One here: (all 1024x768)
[link text][1]
[1]: http://antwrp.gsfc.nasa.gov/apod/astropix.html/ "Astronomy Picture of the Day" Almost exclusively.
The only wallpapers I use at work are photos of my family, especially my kids. Great for reminding me of what I have to look forward to when I get home, and lets me miss them just a bit less.