Depending on the style and what the rest of the bathroom is like, usually tiles around a tub could be either full height or chair rail height which is about half way between the floor and ceiling.

Normally I like to go around a foot higher than the top of the tub depending on the ceiling height. If you have a higher ceiling than 8 feet go halfway from floor to ceiling. In the picture attached I decided to only go 8" high plus the marble cap as we were dealing with a ceiling lower than 8 feet.