Linux links > X Window System
Window Managers for X
A guide to many popular window managers and desktop environments, with descriptions, screenshots and configuration files.
Themes at Freshmeat
It's time to spice up your desktop with themes and wallpapers!
I guess the website's name is self-explanatory. KDE-Look.org features eyecandy for KDE, like wallpapers, themes, system sounds, screensavers, and splash screens.
Again, a website with a self-explanatory name. Eyecandy for your GNOME desktop.
The third sister of the triplets. Eyecandy for your Xfce desktop.