2 Siderooms
1 Backroom
1 extra floor upstairs.
The only thing you can change in the saveroom is the beds. If you have a bed in your inventory you want to use, head to the foot of the bed up there and press "a" - it will ask if you want to change beds.
The room is meant to house up to 4 characters, if they all have double beds, then there is no room for furniture anyway.