I'm a "border person", so for a suggestions maybe add a smaller strip of color around the quilt, which ever color you want to bring out the most and then add a larger border of the black again. If you machine quilt you can use a varigated thread on the larger black border to add color to it. Love the vibrant colors you used in this quilt. Possibly use black or dark grey thread, or even a varigated thread to quilt the body of the quilt.