We built in a little niche on the half-wall that makes up one end of the tub alcove. Here it is when we were drywalling the room:
We've been using it to hold cleaning supplies, toilet paper, and books - you know, the essentials - but other than another piece of drywall on the tub side, it was unchanged since that picture. It was just rough framing, not a finished surface. I finally fixed it up today. The back and sides got beadboard, the top got a smooth-surface luaun plywood, and the bottom got a deep shelf.
I've already lined it up with my stockpile of shampoo and body wash and have stashed the cleaning supplies elsewhere (most of the bottles are too tall with the shelf addition). I left a 3/4" gap behind the "ears" of the bottom shelf.
When I do #59, board and batten, I'll be able to slip a board behind those ears instead of cutting around them. Clever, huh?