First let me say welcome to the Quilt Board!
My first thought would be to follow along with an existing mystery quilt. The other is Merry Mayhem's Mystery Quilts. I believe there is a licensing fee ($55) but there are lots of options. You can also check Craftsy and do a search for mystery quilts, some have a fee but a few are free. Good luck!
https://www.merrymayhem.com/index.html