One of my favorite image “haunts” — www.MorgueFile.com — is offering a specially sized and selected collection of wallpapers for the iPhone.
Personally, I’ll stick with the WickedWordCraft one that I’m currently using, but if you are looking for something out of the ordinary for your own phone… you may want to check it out.
You can also select from the entire copyright free collection of images and size them yourself! I love morguefile.com and often use their images to brighten up my blogs! (You may have noticed).