Changing preferences for new users…

Hard to set the topic here so I will explain it better here: I am creating a base master machine that I will create my master image from and what to edit some prefs for the future users. I have added some stuff inside /System/Library/User Template/ they all work fine. But I want in even more fine grained. Want I want is: Set the default background picture a newly made user gets. Set some Finder Prefs. The system is 10.5.2. And I am not using a Open Directory, but a Active Directory that you can read about in other threads here. Is it possible to do what I want?