Your quilt is lovely and others have given some really interesting ideas to help you make a decision. My thought moves to the binding. I really enjoy a striped fabric binding that is cut on the bias. Whether you decide to make your border lighter (or like the background) finishing it with a striped binding that has many of the quilt colors in it just draws a lovely finish. It also tends to emphasize the lovely quilting you plan for the solid color border-how about a verigrated thread there?