universal settings
 

Is there a way to make changes on one users accounts change all users accounts?

For instance, change all of the users desktops and themes, nautilus settings, etc, all at once instead of doing it to each user. I'd also like to set defaults for the users.

modify /etc/profile file (but be careful). There are also default shell config files, but i don't remember where they are exactly. and that's assuming that every user will use the same shell. Alternatively you can always write a small shell script and a collection of .config files to be copied to every new user's account when created.