I would like to change the default icon set and wallpaper so when a new user is created they have them automatically.
Create a new dummy user, modify its settings to your liking and cherry-pick the changes from .config and .gconf, place them into
/etc/skel. Keep the directory structure intact, e.g. copy:
gconf-editorand try to locate the settings that interest you. The tree structure maps directly to the files involved.
- Be proficient in XML-editing, e.g. a syntax-highlighting editor like geany may show you common typos (In case you want to impose only a subset of the keys in the XML-file, you need to delete the remainder correctly)
- Less is better, too much branding may cause eye-fatigue ;)
While I haven't tested this with more recent versions of Ubuntu, I believe that Sabayon is what you are looking for.
It allows you to tweak all kinds of defaults: panels, background, templates, etc. It is often paired with Pessulus for restricting access to certain features, though is probably more than you need.
Update: It does work in 11.10, and it has been renamed to "User Profile Editor".
You could edit
/usr/share/gconf/defaults/16_ubuntu-wallpapers for setting the default theme/icon set and wallpaper respectively. The file structure is pretty simple. For example, to change the default wallpaper you have to edit the line:
Make sure that the custom wallpaper can be read by everyone and be extra cautious when editing these files as you may damage your system.