For my baby chicks (I have 4) i bought the cat toys that have the small bell in them. The chicks don't play with them that often, but they sometimes roll them around. I also have a long roosting pole the goes across the coop. They like to jump on it to greet me when i go to bond with them. Recently, i put a small swing in their home. None of them have acknowledged it yet, but it'll take a bit of time.
I have found that chicks enjoy jumping and roosting of their water containers. They love to dust-bathe in their bedding (flooring) and kicking their food around. My chicks love to have time outside of their home with me. I'll sit on the floor and they'll jump and roost on me.
Although I'm not 100% sure about this, I think chick/chickens would enjoy a second floor in their home with a ramp. I've noticed that they love to explore new areas.