Here are some hack storage solutions for small bathroom. Add a shelf above the sink for an easy access to the things that you use every day. If you have a mirror in your bathroom, add a frame to combine the design and functionality. Use basic trim if you are not into the traditional look or use molding and paint it with the color that you like best. The great spot for cabinet, some shelves or basket is above your toilet; for toiletries or reading materials.
Hang spice racks to organize all of the stuff that you use every day or hang them on the inside of your cabinets so they are out of sight. Add a coat of paint or color to beautify it. Put a bookshelf above your door for extra storage such as towel, and cleaning supplies. Use a stacked plate rack to make an extra counter storage space when you run out of horizontal counter space.