I have not seen the projects the kids have created but here is a roundup of a few things I would do!
How cute are the stepping stones? I would paint something else on them along with the numbers. My mom painted some really really cute ones when I was younger. My friends and I loved playing on them.
I think the kids would have so much fun making one of these and painting the frame!
This i would let the class paint a plain piece of paper and then put the cut out on top!
There are so many fun projects to do with kids! Let your imagination flow!