I have a complete plastic tub and shower insert. It is all one peice. The proble we have ran into is that our boys who are over 6 feet tall have a tendancy to splash water on the wall. We noticed the paint has started pealing and it starting to mold. We have caught this before it has gotten the sheet rock saturated. I am trying to figure out a way to keep this from happening again. I had the idea of maybe putting tile above it and some what framing in the with adding maybe a tile molding to the outside and kind of framing in the shower/tub insert so it will look like something that was planned rather than just putting tile up there. I would also maybe be able to move the shower head higher to help with the over splashing as they have to bend under the shower head. There is 37 inches above from the top of the shower/tub closure to the ceiling. If anyone has any ideas about this, or if think the idea i am thinking please feel free to post. I went to our local home Depote and kind of got the run around of no real good answers to my questions. I can post a picture if need be of the area.
Probably more than you want to get into but it may be worth your while to replace the sheet rock above the insert with a water resistant backer board like Durock or Hardie backer. You would want backer board behind your tile, not sheet rock anyway. Tile over sheet rock would create more problems than it would solve. I'm sure you could find some sort of primer/sealer/paint combination less resistand to water also.