I don't see much value in the collapsible headers, since we have so few sub-fora, but some people might find it useful, I guess.
I think a decent outline of the Tusk wouldn't be bad, but it's really a toss up between that and the Circumfix, I think either is fine.
I do prefer a darker color theme, I really liked the old board's black, gray, gold and red theme, but again, that is just personal bias.