I just wanted to take a few minutes to give this site a plug. I've been an avid fan of the wallpapers produced by Ryan over at Digital Blasphemy for some time now (and in fact, it's the main reason I made my Wallpaper Changer app - so that I can have a different Digital Blasphemy wallpaper every day!) I often get comments from friends and coworkers about the wallpapers I have, all of which I got from Ryan's site.
Anyway, if you haven't yet, check it out. It's got a great selection of free wallpapers, and the member's section (which is a bargain to join - I did!) has even more. Plus new wallpapers regularly - what more could you ask for?