well obviously, all of the planning would take place on the shadowbox.
i was never a part of the brigade, so i'm only here to be excited and help however i can, but it would be cool if there could be a book created full of stories and memories of the brigade, only available to brigadiers, to be debuted at the show. it could be set up like a yearbook, and at the convention, you could get everyone to sign it!
more generally, something similar could be done for the whole shadowbox. a yearbook-ish thing with a history of the community, and then anyone with x number of posts gets added in automatically and everyone else by request. Donations could get bonuses, etc etc.
a celebration of the dresden dolls is a celebration of the community they created and all of the wonderful things that happened as a result. any events taking place at the convention would be open to anyone but there's no WAY that, even if nothing was specifically set aside to be "exclusive" to 'boxers or brigadiers, they wouldn't receive natural bonuses anyway. I'm sure so many people would be happy just to be a part of it.