small tiles, no mesh backing, 72 hour flood testing, ceiling tile should be tipped at 2" per foo to prevent water dripping on users, darker tile easier to keep (looking) clean, traction necessary!, curved ceilings require smaller tile, tile better than natural stone but stone is more comfy to sit on a slab bench, make sure drain line is big enough (2" drain not big enough for 2 showerheads), paper or film-faces glass tile best,