I have started a series of screen backgrounds - they are posted at my flickr site.  Hope you will take a look and use some of them - feel free to use them for fanart as well and to share,  just please give credit to:  nmcil whedon world gallery.

This link (willow image) will give you access to all of the desktops, click on the thumbnails for link. 

First time posting an image link - hope it works.  Love reading all the wonderful work here

http://www.flickr.com/photos/nmcil/763214632/