I think moderation should be stricter. Posts with close to zero content (f.ex just "lol") should be deleted. Less crap to sift through when reading through threads.
Not wanting to go all nazi, but there could also be a limit on the size of signatures. I know there's a limit on how much text (and code) there can be in a sig, but it doesn't take much text to link to a large picture or two. Maybe there's a way one could have limit in lines instead. I've seen it on other forums, but I don't know if it's possible with vbulletin.