My student enjoys music so I pulled up a piano app and designed an overlay. I purchased the protective cover at the Dollar Tree. I left the cover intact and used Wiki Sticks to create the design. You could use puffy paint or hot glue. I wouldn't suggest using the hot glue while the overlay is on the iPad.
I use my personal iPad with my students. It has the a cover with a magnetic keyboard. I slid the overlay between the case and the iPad. Store the overlays in a binder using page protectors.
I look forward to making a few more to use with my students.