When I thought of some unifying thing which exists beyond ethnicity or nationalism I couldn't imagine anything better than clouds.
Clouds are essentially formless, but we see so much in them. Children can see any number of characters, animals, or locomotives in these puffy white expanses. They can even represent dreams or thoughts; as in a comic's "thought bubble".
If one is trying to activate a child's imagination, aren't the wonders of the sky a good place to look?