Our bathroom is big by some standards, but not huge.  We found that having two sinks definitely helps with marital bliss (although we've also lived with only one just fine.  This issue is when we both have to go to work at the same time).  Our cabinets are sustainably harvested alder, a local wood which we liked better than we thought we would.  We used the same counters as the kitchen (Cambria) with recessed sinks so they're easy to clean.  In retrospect, we probably could have put a small skylight on the outer edge of the room and had better daylight.

The floor is ordinary Terra Cotta tile with a 300 watt electric heat mat under it, that we use only in the coldest months to keep the floor from feeling cold.

The window trim is sustainably harvested pine.

When we travel, we use our shower as a automatic plant watering system (left), which is just a short drip irrigation system. Our shower tile is grouted with an epoxy grout, so is less prone (but not immune) to mold problems.
We opted for a sauna instead of a bathtub, because all the heat goes to the house, and it is just as good for stretching achy muscles.  Our Sauna is made largely out of reclaimed cedar that came from the ceiling of a house that was being demolished.