The bathroom walls will be a material called “microcement” with has a smooth, stucco type finish.
Here a couple of images of the tiles I’ve seen to combine with it. The first is the floor tile with a checkered border and one of the two mosaics will go on the built-in counter with the sink.
I love this sink for the asymmetric effect it has when when you walk by:
P.S. Sorry about the bad image quality – only had my iPhone with me (no flash!)