Based on "Debian Aqua" by naazgull (http://gnome-look.org/content/show.php?content=17496).
I made a few changes:
Removed "Debian" text
Made the swirl less translucent
Replaced gradient background with the Mac OS X Panther default background (had to scale it up; if anyone could put in a native 1280x1024 copy of the Mac Panther background, that would be great; I couldn't find a larger one on Google)