Engine

The most configurable Gtk2 engine is here.
Murrine is a Gtk+ engine, written in C language, using cairo vectorial graphics library. By default it comes with a modern glassy look, elegant and clean on the eyes. But it is also extremely customizable, and allows the user to achieve an incredible variety of styles.
See what is going on in the svn!

Links
Source Code: http://download.gnome.org/sources/murrine
SVN: http://svn.gnome.org/svn/murrine
Bugzilla: http://bugzilla.gnome.org