A friend of mine rented port-a-potties when she held a wedding reception at her house, so her septic system wouldn’t be overwhelmed. She made one a “ladies” room, and one the “gents”. She went all out and decorated the insides of each in interesting ways. The “gents” room was wallpapered in antiqued newspapers (they looked old and yellowed), so there was always something to read. If I remember correctly, I think she had a container with cigars and matches in there, too.
I would shape it like a rocketship…with portholes. Just cut the front and back panels in the shape of a 50’s rocket and paint it. Of course, use that dark filtered film in the portholes for privacy.
Or, you give it a dome and paint it dark inside and then put stars in it…a planetarium loo!