Go up with storage and hooks, bins etc. over the toilet install a shelf or hooks to hang towels or clothi got get dressed. Try not to clutter it up too much. Floating shelves or box like shelves can help.
Pedestal sinks can offer room if you consider eliminating a vanity. Also elevated unconventional storage can be effective.
The back of the door provides a great space for organizing your toiletries. A clear shoe organizer works best. You can also put a shelf above the door. And, of course, use the space above your toilet by putting up shelves or even an over-the-toilet cabinet. Hooks work great for hanging robes, towels, etc.
I agree with Cindy! Utilize the back of the door. We have all of our towels hung on the back door
Go to the walls with shelves or cabinets. Don't forget over the door as storage for items like extra toilet paper.