How can I add a theme to the Appearance settings tab in 11.10

Solution 1:

I took a look at the source code for gnome-control-center (specifically the cc-background-panel.c file) and found the answer. The list appears to be hard-coded in the source:

static gchar *themes[] = { "Adwaita", "Ambiance", "Radiance", "HighContrast",
    "HighContrastInverse" };

This was added by Ubuntu (in 04_add_theme_selection.patch) to the original gnome 3 gnome-control-center source. It appears that they did not plan to allow anyone to add 11.10 themes at this time. Presumably the list will be editable or generated dynamically in future versions of Ubuntu's theme selection patch.

Solution 2:

If you have root access to /usr/share/themes you could also recycle one of the hardcoded theme names for your experiment, e.g:

sudo mv /usr/share/themes/Adwaita /usr/share/themes/Adwaita.old
sudo ln -s /path/to/your/theme /usr/share/themes/Adwaita

Obviously your theme will show up as 'Adwaita' in Settings -> Appearance. Not very elegant, but functional ;-)