Normally I'd want to say "theme" here, but I think referring to Atahualpa theme themes would just get ugly and confusing really fast.
Basically, allow saving of the current settings by name, and allow changing of the "active" setting set. The "active" set could be identical (even in the settings database table) to how it is now, with a change of set triggering a rewrite of the active values in the database. Alternately, there could be an extra layer of "which setting set" that would then change which set of options was being read from the table. The second option might eventually allow specification of different setting sets for defferent pages/categories/whatever, so you could have different appearances within different areas of a site. You could also think of the first option as a named-backup-and-restore functionality if you'd like - there's not really that much difference.
My thinking on this is that it would make it much simpler to experiment with appearance if you didn't have to worry about separately backing up your settings to be sure you could get back to your previous layout if you didn't like the changes.
ThemeFrame may have this, and I'm figuring on experimenting with that as well when available.