Use the normally wasted and problematic water tank space sides for storage
Tiny bathrooms are tough to design because they are compact; save money on materials for using less material- but small bathroom is small, and nobody likes being cramped. You can start decorating your space by avoid hanging anything that sticks out from the walls especially in very narrow bathrooms. Just go with built-in toilet paper holders and magazine racks. Also try to avoid decorating shelves because it takes away precious square footage.