I would love a backyard area where I can do whatever with. I mean some of the Halloween items would look great out there during fall. Also more rooms would be more then awesome~
I have the largest house and it's still to cramped. I would be happy with proper dividers to section of the house but this would be a lot nicer.
Maybe also have a part of the house that is like a back door but takes you to your friends house. Like you click on the door and a list of your friends comes up and you can go visit.