I was the first dissenting voice. The more forums you have, the more forums you have to check.
The klov.com forums split into about twice as many forums a while back, and posting went down dramatically when it happened.
It's a fine line to balance: If you make too many subforums, you'll splinter/fragment the audience TOO much, to where each subforum dies a bit, but having ten million threads in the Main Forum is a problem too. We had a very similar problem at Something Awful and learned all this as we went.
The more "specialized" a subforum is (and an artwork forum is a great example of this), the better it will work both for that particular subforum, and for the overall forum community. So I still say "yes".