Ubuntu (using GNOME) has the following customisable elements, which change its look and feel:
-
Wallpaper (GNOME or compiz)
- Metacity window border theme
- GTK widget theme
- Icon set
- GNOME splash image
- Mouse cursor theme
- Grub bootsplash screen
- Usplash bootsplash screen
- GDM login screen
- Qt theme
- Emerald theme
- Panel
- Fonts
- Sounds
- Docks like AWN, cairo-dock...
- Screenlets, widgets
- Screensaver
- Wine colours
- Program themes:
- Firefox
- Opera
- VLC
- Java(?)
- OpenOffice.org(?)
(Add anything else that you can think of here)