In my search for a cool wallpaper I came across this site some time ago. This is what they write about themselves:"deviantART is an online art community for artists and art lovers to interact in a variety of ways, ranging from the submission of art to conversations on a number of topics. In its purest form, deviantART is a means for expressing ones-self in a variety of ways."
Some of the submissions are really cool, so go check it out!
This is some of the stuff you'll find on deviantART:

Designs, Flash, Fonts, Icons, Indy Art, Interfaces, Photography, Pixel Art, Poetry, Prose, Screenshots, Stock Photos, Textures, Themes, Tutorials, Visualization, Wallpapers...

Signing up is free, but if you decide to subscribe to the site you'll get some extra advantages: no banners (e.g. faster surfing), exclusive content, private forums...it's 3.95 a month. I haven't signed up though, but maybe I should,- just to support their effort :-)