Here are a few ideas:
1. Mirrors can make a small room look double it’s true size. Install a mirror that runs from the countertop to the ceiling, and from one wall to the other. In a small bathroom this is very workable. The effect is far different than a smaller, wall hung framed mirror.
2. Layout: Experienced remodelers can help with arranging the toilet, sink and shower or tub/shower. Each home will have it’s own quirks and has to be evaluated based on what is already there; doors, window, locations of plumbing piping. If cost is not an issue, you can do pretty much what you want, but most people do have to include the budget when making decisions. Keeping the plumbing piping where it is will keep costs down significantly.
3. Storage: Get things off the floor; think vertically. Shelves installed on or in the walls, between studs. Keep extra towels in a closet outside the bathroom. Just keep what you really need in the bathroom.
4. Small showers work well; try out a few styles and sizes at the local bath display store to see what you are comfortable with. There are nice corner showers that can fit neatly into that unused corner. Have glass shower walls to keep the space visually open.
5. Pedestal lavs can be installed to accommodate really tight spaces, or just to open up a room.