I'm just weird enough to think that the design could be continued as it is, then add a nice border to frame it. Many years ago, when my eyes could see the holes in the canvas, I really enjoyed doing bargello needlepoint. Designs which continued up and/or down the full width of a canvas were intriguing, and they certainly did not have to be a centered design. The final word is this: it's your quilt -- and a wonderful one -- so do what your eye and your heart are telling you to do with this. It should turn out to be a masterpiece!!