I agree with PP (seems I do that a lot! Great minds think alike). To me the dark border changing to chevrons draws the eye to both the center and those fabulous cornerstones. What I would do to give it more continuity and flow is when you quilt it, quilt "ghost" chevrons of the exact same dimension as your pieced chevrons in the dark mottled black fabric. You could even get brave and quilt them in the colors of burgandy, blue, forest green purple.