This certainly would be a fun pop to the sauna walls.
This "natural" outdoor hot tub would go great with my Japanese garden theme. It is almost like a hot spring. I'd get rid of the ugly fence in the background though and have a lot of flowers, trees, and bushes.
Here you can see what a great light fixture can do for a (bath)room. Think larger pattern tilework for more impact
Image 4 of 72 from gallery of Snow Hotel / 1990 uao + Archigroup MA. Photograph by Sun Namgoong