Goto User CP (on the navigation bar :
http://forums.armageddononline.org/usercp.php )
and goto "Edit Options".
Scroll all the way down and one of the last options should be "Forum Skin"
You can change it at any time.
Additionally, Most of the forums skins have a "quick" switch all the way at the very bottom of nearly every page.
Change 'em any time.... however... some functions don't work with other skins.
The only official skin I keep updated (or at least try to) is the defauls "Main site" Skin. Probably won't change that until vBulletin offers some sort of global template hack.... which I hope isn't that far off.
-MM-