a murphy bed that folds up and has closet space! its like a bedroom in a cabinet. I would totally do this in a room with multiples. fold the beds away and its a play room! (also when they move out, you just fold their bedroom away until they come visit!)
The One Space Everyone Needs In Their Home Is A Sanctuary: A window offers a lovely view, and sunlight has been shown to improve mood. The second-best option is indirect lighting -- the key is not to have glare.