I have a toy box full of different toys for my buns. At any one time they have four toys to play with, then every few days or so I take those ones out and put fresh ones in. This makes sure that they don't get bored with the same things. Plant pots, tunnels, little step up steps, boxes, childrens hard plastic rattles, treat balls, jingle balls, willow sticks to chew, willow balls to throw and chew, childrens hard plastic cars.....charity shops are a great place to find bunny friendly toys. Perhaps have a look at the websites for Willow Warren and The Hay Experts for more ideas.
Best of luck.