I can't remember the last time I browsed through a desktop + wallpaper repository site and actually felt compelled to use any of the offerings. Sites like The Fox Is Black's Desktop Wallpaper Project supplanted the need for looking at such collections. However, Solid Base is worth a gander. I love that you can browse by color and that there's no shortage of space offerings.

Be sure to snag this, this, this and this on your way.