Oh boy, you have treasures!!.
My first thought would be to cut plain blocks big enough to sew the handkerchiefs to, than use sashing to make them all the same size. Make sure when you sew the hankies to the background to not interfere with the decor of the hanky. Tough to do. I'm going to get ahold of my SIL and get a pictures of a custom quilt she did for someone that was similar.