By "tub liner" are you referring to a fiberglass tub with a fiberglass surround or are you going to install a tile surround?? Either way the surround normally stops at 6' from the floor. The shower head protrudes through the wall 4 or 5 inches above this. If you are tiling, you could extend it to the ceiling (and it should be applied to backer board, not directly to the drywall). A fiberglass surround is a fixed height with drywall above to the ceiling unless you want to add tile on up to the ceiling........