Is it possible to restrict users so they won't be able to change the desktop, i.e., background image and icons? I'm running the latest ubuntu (11.04)
The background is a setting in gconf-editor:
Pessulus enables the system administrator to set mandatory settings in GConf, which apply to all users, restricting what they can do, which may be of particular usefulness for kiosks (internet cafes, for example). Examples of what can be locked down are the panels (no changes in the panel configuration are allowed, locking their position and their contents), some of their functions individually (disabling screen locking and log out), the web browser (disabling specific protocols, arbitrary URLs, forcing the user to be in fullscreen mode), among many others.
Pessulus <- to install.
I do not know Pessulus well enough to know if it also locks themes and iconsets. If not you could delete all the other iconsets if you want to and make the directory non-writable: adding new themes would result in a permissions error.