Yeah, but that's one of the best parts about vBulletin. And 150x150 wouldn't match with the avatar limits I have here as a Tier 6, so I couldn't globalize my avatars.
How about this:
Members = 130x130, 130KB
Mods = 150x150, 150KB
S-Mods = 180x180, 180KB
Admins = Unlimited (through upload via Admin CP)