Moderating avatars and location isn't something that can be done with the stock code. However, you can limit the max width/height of avatars and anything over that will be scaled down to that size.
Login names and Display names have to be unique, so there's no real way to allow for users to have the same display name if there names are exactly the same.
Signature limiting is still an issue that needs to be addressed. There really is nothing currently in place to keep people from posting obnoxiously large images in their sigs.
