I have never seen Disney tiles but if you go to Pintrest you can find some you can make.
Do a search for Coaster tiles. They give directions on how to seal the tiles to use as coaster so I think you would be able to use them on the walls. I wouldn't use them in the tub or shower but they would most likely work on the other walls. Maybe use the plain ones in the shower and on the walls with a few character tiles interspersed.
Or you can go to a ceramics studio and paint your own then have them glazed. Those would work in the shower. You could probably pay for the person who runs the shop to do them for you too. Ask if they have kiln safe decals with Disney characters.
