Whatever you do, don't sneeze
After looking at the pieced quilt, I relaized that it would be set off very nicely by a set of three borders: two solid ones surrounding a slim, pieced border of all the fabrics used in the strata.
Bonus: this idea would allow me to use up many of the scraps I incurred from doing a pattern with many curves. About 90% of the pieces you see here were cut from scrap. This pleases me immensely; I don't like wasting fabric.