Hoping the below pic will help explain what I am thinking off.
Currently there is a bathtub and then next to the bath tub was a closet that was accessed from the outside of the bathroom. We have closed off the outside access and tore out the crappy framing for the closet. I want to add a cubby/shelving unit (in red) and make the left side of the unit be the other wall for the tub enclosure. Rather than take it to the ceiling I was thinking of making a large ledge for shampoo and all the other junk that my daughter has (that seems to breed and multiply over night). My concern is pooling of water. Can I frame this with a slight downwards angle to the shower or am I worrying about nothing.
The pic is as if you were facing the tub. Yellow is tile and red is the new closet/cubby.