When it comes to the file size, a good rule of thumb is the load time and common sense. If it's too big, then other members will notice and report it. Then SigSanta will be involved in the removal.
Maybe we need a "testing sig" thread where members can test their sigs before SigSanta takes care of 'em. Would that be helpful? We'd have to discuss how to handle that. The reason that I ask is that the first time a sig is too large, it is removed. The second time, it is removed and the privilege suspended for one month. The third time, the sig privilege is removed permanently. Though some may think I like removing sigs, I'd rather not.