Have seen where high end RV remodeling places use a set that won't get hard over time and epoxy grout. All material is important because the movement/flex of the RV will destroy regular tiling materials. Most of the materials are more expensive but the grout can be made into any color imaginable and also reflective. Looks more like plastic than regular grout. Will not stain like grout since it isn't as porous. Floor heating elements can even be installed. It's a very appealing thing to do and would make a world of difference in look of the interior.