Great idea RE the twin mattresses. I also love the tree pictures on the wall! Love to display kid-made art in a kids room! Two twin mattresses, some plywood, and a great playroom that doubles as a guest room or sleepover room.
I love the wallpaper on the ceiling idea and the heart picture thing on the wall better than this couch thing. The pic says this couch thing was in a girl teenager's room. I think that is a bit much for a teenager's room.
Simple stack of multiple fabric-covered foam pads. makes a cushy "sofa" in the playroom, and can be pulled apart for multiple sleepover guests, movie night pillows, or tumbling games, etc. (they have fabric covered foam mattresses at Jysk)