Built in storage. This is pretty much our attic bedroom! That's a lot of storage and nice touch is the niche for a TV. It may be possible to use IKEA chest drawers to acheive this. Or find a talented carpenter.
two twin beds. A curtain hung from that cute heading would disguise your "bedroom" if you chose. A curtain would work above as well for either a bed or built in shelves and hanging space for your clothing; I really love the idea of deep, built-in beds