Writing about web page http://www.deviantart.com
Here is a site that is simply the largest art gallery in the world, with currently over 8,000,000 pieces of art of all category and genre. There is also a huge selection of the art available to buy as variously sized prints, as well as mouse mats, mugs and that kind of thing. Most is reasonably priced, excluding the few looneys who try and sell stuff for hundreds of pounds (and fail miserably). The Prints themselves are really high quality, if I compare them to the poster sale that takes place in the Cooler now and then, they are thrice the quality of the artprints that were selling there for £7 and are usually available in glossy, matte or lustre prints. I highly recommend the lustre ones as they combine the sheen of the glossy ones with the texture of the matte.
There is literally something for everyone, from Photography to Anime and Pencil to paint. And a huge range of stuff comes in the right size for your desktop. You don't have to buy the art to appreciate it.
I suggest you start here – http://grigari.deviantart.com because it's my gallery :D;) With some reasonable prints I may add ;)