It's all in the details, folks. If you want to design a small bathroom on a budget -- but might not necessarily be able to do much with a demanding landlord -- you can start with tiny details that won't cause much in the way of damage: replace fixtures, try new lighting methods, and use peel-and-stick tiles to transform the aesthetics. In terms of functionality, you're going to want to make sure you have plenty of storage space at the ready, and don't forget to look up.