How can you design a hip bathroom that is very small and has no windows?
Paint it black. Seriously.
If it's already windowless and tiny, then make it dramatic. Just use it for bathing and having wild sex in the shower. Don't plan on doing your make-up in there. Install candle sconces and lighting on a dimmer and douse the place with perfume and make it a sort of wet romper room for you and the ones you, uh, love.
Get a low dresser for your bedroom, prop a mirror on it, get a cool lacquer tray for your primping essentials and get ready in your room. My get-ready station is actually my office, not my bathroom (because my upstairs bathroom has a toilet in the tub and my downstairs bathroom has no storage for my Jil Sander no. 4, my hairdryer, or my make-up, for that matter.
Readers - got anything to add to this?