Here is a really great list of ideas you can do with a tiny bathroom. Just because a bathroom lacks square footage doesn't mean it can't be both functional and beautiful.
Display Your Accessories on Dishes
Built In Shelving Unit- Walls, which are typically four inches thick, offer a place for additional storage whether it's a recessed medicine cabinet or open shelving.
Hang Towel Bars on the Back of the Door
Hanging Baskets Storage
Hide Clutter with a Sink Skirt
Store Towels in a Wine Rack
Above the Toilet Cabinets
Cabinet Door Storage
Organize Bathroom Products with regular wall shelves from Amazon:
Use a Rolling Cart