you can make your own wallpaper from any image easily with photoshop, paint.net, gimp etc.
just make a new image the size of your desktop... fill it black or whatever.. also open your desired photo.. select all, copy then going back to your black image, paste. drag it in to place, save it and voila.
this site has some beautiful wallpapers and you can download them at any resolution:
http://interfacelift.com/
i have probably 150 superb wallpapers from there.
use it in conjunction with this tool:
http://www.microsoft.com/downloads/d...displaylang=en
and every 15 minutes you have a new work of art on display =)