It looks like you have nice wide borders. It's a bit of work but what I have done in this situation is take off the two side borders and quilted the quilt without quilting the top and bottom borders. I then reattached the side borders, check to make sure they are still the right length, you might get a little quilting shrinkage. Then I just did straight line quilting in the border making a square framing effect. Good luck.
Your quilt is beautiful!