Since a bookstore is a retail establishment, your restroom becomes public whether you want it to or not. Especially if you have a children’s section. Take 300 seconds today to make sure that it’s ready for visitors.
I suggested this task once before, and I proposed taking advantage of the “captive” audience by placing items on the walls. Event posters. Children’s story time announcements. Publisher provided posters. Even signage with a long shelf life.
If the items on your walls have no expiration, it’s still a good idea to change them out. You could create a rotation of “seasonal” signage, or just take the opportunity to be creative every 4 to 6 months. And if you don’t want to mar your walls with an abundance of tape, consider hanging an understated frame. Then any signage you create can be produced to meet those specifications.