It’s an appealing question. However, do you truly need to put something on the wall? When you look at the historic publications from the past, you will see that they have constantly applied something on their wall space, even when people lived in the cave, they painted their wall surfaces and put some simple ornaments such as flowers.
Children often have their own universe – the land of dreams and imagination. Although it could be not easy to enter this zone, the adults can help their kids to realise their fantasies, at least in some part.