Soft, muted textures will produce a becalming effect while lowering your body temperature. Avoid tiles, with their glaring reflections. Clearly, a harsh, naked bulb, reminding you of a torture cell, is to be avoided. Skylights are always a tempting proposition, but only if facing north, so as not to surprise you with a sudden burst of sunshine. Bathroom is your ashram, and rude awakenings are to be avoided.
Art is always welcome.
There is no reason why you should check in your taste at the door. We imagine that a quality Rembrandt reproduction is worth a hundred Jenny Holzers, but we may be erring on the conservative side. Or, perhaps, you want to do The English Patient and decorate the walls with Saharan vistas, caravans specking the horizon, and install a small sandbox instead of a toilet-paper roll. Neither design reflects our taste, perhaps, but you are entitled. Another item we should neither sneer at nor dwell on undule is the choice of toilet paper.