Beautiful Dresden Plates!
Do you have enough of the fabrics to do borders?
Maybe a sort of narrow border - the size of one of the strips in the sashing (perhaps of 30's repro fabric) next to the pinwheels & sashing, then another pinwheel border with pinwheels alternating with solid white blocks, then another fairly narrow border of a second 30's type fabric.
Don't know if that will get it to the size you want or not.