I’ve included the backgrounds with the theme packages, hence the size of the files. Just extract them to ~/.themes (notice the leading dot), and they should work fine. All of them so far are simply hacks on the Xfce engine, as it seems to be the best balance of usability/aesthetic appeal. Click on a thumnail for a full-screen image, or on the theme name to download.
Rakka: Inspired by Haibane Renmei
Regatta de Blanc: background courtesy of Propaganda.
The window manager in the screenshots is Xfce 4.1, which does a good job of combining features like right-click root menus and middle-click wiindow menus with full Gnome integration and a much improved desktop. The window theme is Operational.
NP:The Long Walk Home at Midnight, Xela