An elegant gentoo background. It is transparent, as seen in the screenshots. This one is actually realy neat, so if you run gentoo (or just like it), you should try it. As seen in this new (blue) screenshot it works nicely with 1600x1200 resolution aswell. I'm currently working on a GDM-theme based on ThinkFree to go with it.
It is based on a wallpaper by Brian Wigginton: