There are software applications available including the reprint rights for creating this type of book, or of course you can use the customer's and your imagination to create original stories.
Roll your cubes and make an imaginative story based on what the cubes land on, and the brilliant thing is that you'll get a different combination every time you roll. Endless ideas for stories!
Many might write off the space, saying lower, angled ceilings make the room unusable ... and coloring books. If you don't ...