I really like Cannibal's solution. I've never felt comfortable attaching much to the side wall 2x4's. Plenty of folks do it with success (usually by spanning a short piece of wood across several wall joists) but I just don't like it much. It puts several hundred pounds (or more) of force pulling in on walls that weren't meant for that direction of pull. I much prefer forces pulling up or down, exactly like what Cannibal has.
Two of my kids hang full time indoors and we use the Vario hammock stand for them. I'd definitely recommend those for the looks and simplicity - or a TurtleDog stand if you need the extra height. The Vario is great but it doesn't go high enough (without some special extensions) for an 11-foot hammock, which I really like. A portable stand allows us to move things around easily and not create any permanent fixtures in the walls.