Just search your resolution on google and I'm sure you'll come up with a site that has wallpapers that size.
Here's one if you're a Cuthbert fan :
http://www.cse.ohio-state.edu/~sheik.../ecuthbert.jpg
Here's another link that was posted in OOT a couple months back :
http://www.vladstudio.com/duals/
And another :
http://users.telenet.be/jbruyndonckx/wallpaper.html