How to install vinyl tile over tile in bathroom?

if the first layer is ceramic type tile, you would have to put a sub floor over it, then the vinyl squares. if its vinyl over vinyl squares, you need to lay out the tiles so it covers the "seams" of the previous layer. the vynial is flexible, and will sink into the previous grout lines, hence the sub floor.

Hi - you may want to consider if this is what you want to do. It will cause there to be a big transition between the floor in the hallway and the floor in the bath.

How about the walls? Floor to ceiling tile in disco yellow. Thinking about replacing with vinyl slats.