Most computer users, of course, are interested in customizing their desktops with their favorite wallpaper. However, there’s an overwhelming number of sites to choose from, some offering better quality backgrounds than others.
Here’s several sites that provide sources of quality desktop wallpaper:
MacDesktops: While it’s dedicated to providing wallpaper for Mac users, users of other operating systems can also use the wallpapers provided here. The wallpapers are subdivided into various areas: cars, sports, movies, music, nature, animation, holidays, the various ranges of Apple products (iPods, iMacs, etc.), and so on. A few wallpapers in my opinion would fall under “not suitable for work” (the “show some skin” category, almost all of women), but the vast majority of the wallpapers are suitable for everyone. Also useful is that each of the wallpapers are offered in various popular screen resolution sizes.
Flickr Creative Commons: The online photo sharing site Flickr offers in a Creative Commons section thousands upon thousands of photographs that one can download as desktop backgrounds. Creative Commons is a special license one can apply to photos (or other created materials, such as articles, etc.) that allow for various usage rights more liberal than the standard “all rights reserved” copyright.
http://www.flickr.com/creativecommons/ (Flickr Creative Commons photos)
GNOME Art: GNOME, the popular desktop environment for various Linux distributions (and my desktop environment of choice), offers on its website a section for downloadable backgrounds. The wallpapers included are free for anyone to use, and are mostly licensed under Creative Commons licenses. A few, however, are listed as either being in the public domain or offered under GPL (a license more associated with open source software than images).
If you’re interested in wallpaper for your iPhone or Palm Pre (which both have the same screen resolution size of 480×320, and thus can use the same size wallpaper), I’d also suggest:
iDesign * Pre: This site, though not updated in some months, offers a variety of wallpapers in various categories (cities, sports team logos, nature, anime, etc.).
iPhone Wallpapers group on Flickr: This Flickr group offers thousands of iPhone wallpapers, though since there’s no subcategories, it may take some time browsing/searching to find backgrounds of interest.