Would you be willing to do more applique... trailing flowers/vines? you might like a solid sashing around what you have now and then a 10" wide border w/ the vine-type appliques. it need not be very elaborate... if it were, it'd detract from the center. Seems like the borders need to be less busy than the center and this would be a way to accomplish that.
ETA..previous poster and I were answering at the same time and I see she said the same thing!