Twins stepping stone

We used cement mix in a pie pan or bowl. Then were allowed to use pictures, beads, and all sorts of material to make our stepping stone our own. I did not know what to put so I just make a Twins logo and called it good.
For an extension you could have each student make one to place outside the school grounds or somewhere near a park with permision. That way each student could look upon the whole class's creation and enjoy the work.