We can take our pick from bathroom wallpapers, micro concrete,
polished plaster, vinyl flooring, Moroccan - style
tadelakt and many other wonderful, waterproof creations.
I'm a huge fan of the Moroccan plaster finish
tadelakt — applied seamlessly, it results in a beautifully smooth surface, free from grout lines — or alternatively,
polished concrete, because it doesn't matter if it chips slightly as it just leaves a lovely crumpled effect.