I think floor to ceiling tiles in a small bathroom can look quite nice. You may want to think about using a combination of tiles to add more interest and texture to the room.

Cooler tones and ample lighting are two ways to make a space feel larger. Furniture pieces with slim legs and details that are lifted off of the floor a few more inches, give an airy, spacious look. You might also consider incorporating reflective surfaces such as a mirror to catch light, or a polished lighting fixture to draw the eye upward. Hope this helps--good luck!

You don't see this much in photos. Usually the mouldings are painted the same colour as the ceilings which of course lowers the ceiling height even more! Vertical stripes would be fun!

Having only 4 feet above your face sounds tight to me. Guess you could have a couple of people hold a thin piece of plywood at that height as you lay on the floor. Think I would move the doggie den somewhere else and use a couple of those feet for the sleepers.