I think bill is one the right track. I have, as well as others, talked about the old SkinzBrowser app that skinz.org had. That seems like it would be the best way if you were set on this idea.
How this could work:
For registered users - SkinzBrowser would allow unlimited downloads and access to WC features and maybe add a bit more as an incentive to register.
The question here is, what if someone has a NS/WS registration but does not have a Stardock registration? Do only Registered users of Stardock Apps get to access unlimitedly? You do also house skinz for NS/WS.
For unregistered users - Access through WC.com but would only allow for (X) amount of downloads per day and maybe limit their number of postings to the message board.
A few pros and cons:
Con: This would limit the interaction with WC and could cause it to become less popular and quickly become an elitist forum. I have seen many skinz that are by unregistered users that are fantastic. You could loose this audience from uploading their skinz here.
Pro: This could incise people to register Stardock (WinSTEP?) products for the other features that WC could have to offer on the "registered" side. It would cut down on bandwidth.
I am a registered user of HoverDesk, ODNT, WinSTEP and Talisman so this wouldn't really affect me. But like MooShoo & Paxx said, allot of this community is still under the blanket of their parent/spouses

and do not have the luxury of dropping the $$$ whenever they want. Do you really want to alienate these long time faces?
0.02