The bathrooms have tile in the shower up to the ceiling. There was no crown molding in there before. I thought it would help update the rooms. Does the molding stop at the tile, or go over it, to surround the rooms?
C.M. on tile would look weird to me. I assume you only have tile to the ceiling at the shower stall, so it should still look good by stopping at the tile and cutting a bevel to come down to the wall. Either use the plastic molding or very carefully seal all sides of wood molding prior to installation and seal the interphases with ceiling and wall with caulk to prevent water infiltration behind.