Definitely do not use stacked stone in a shower. It is not designed for a wet environment and it would be nearly impossible to keep the water from getting between the stones. I think you are on the right track with similarly colored tiles, maybe something a little larger scale, that would pull those warmer colors out of the stone wall behind the vanity. Start with maybe some 6" x 6" tiles and see how those look. Have fun!

There is a tile that comes in 6 x 6 and 18 x 18, 24 x 24. It is called Keystone Wind. It is a beautiful travertine look porcelain Italian tile that has cream and gold and white in it with definition. It is not your usual flat looking tile. It has texture. I feel it would look really nice in this golden bathroom for floor and shower.