I'm interested
timeth!
About forum separation...
Yes we have to be careful => in my humble opinion, it should be very easy for new people to get into the artwork-group (if we place it elsewhere).
In all the possibilities I looked through, I never found a suitable gallery with latest additions.... (where people can vote directly, add ideas etc.... => something like that would be perfect; but I think that requires a custom made website -- and my exams are starting within 2 days

)
The last thing we're looking at, seems better than the others - because it HAS a list with all latest files... (but timeth's suggestion is still coming

)
(however, I'm going to have an extra look at the Google Sites option, because you can modify the behavior very much, with gadgets, and custom made things I think

)
About transparency...
=> it would be perfect that the external visitors only can view previews, but that the involved artists can share their designs, artwork, ... (in this case the full files)...
:: visitors can vote for the previews (and add ideas)
:: artists can work together on something (who has some time now, someone else tomorrow (or someone else with a little other idea), etc...)
But maybe that's just too much work for the artists (uploading 2 things, ....)
I think the final solution should be something as simple as possible

(I think we all agree on that)