/usr/share/themes
system themes directory
View mutter themes
mutter-theme-viewer [THEMENAME]
mutter-theme-viewer allows you to preview any installed Mutter theme.
When designing a new Mutter theme, you can use mutter-theme-viewer to measure the performance of a window frame option, and to preview the option.
Name of the theme to be shown (Atlanta by default). It is case-sensitive.
/usr/share/themes
system themes directory
/usr/share/themes/*/mutter-1/mutter-theme-1.xml
theme specification file
Unchanged in 2 releases since Debian 6.0 (Squeeze).