Don't build the interiors of any private buildings (houses, barns, sheds, etc). Buildings/landmarks that are public and are iconic should have interiors done. Any place that is openly available for the average person can be built. It is completely up to you whether or not to build it.
Place such as lobbies, waiting rooms, and churches can all be built (if accurate references are available), but refrain from building any private interiors such as homes, offices, government buildings, and hotel rooms.