I recently had the same problem with a quilt top I was making. An experienced quilter told me to do sashing with cornerstones. I didn't think I would like it, but when I completed the top, I was really happy with the look. If you have more of your cornerstones left, lay a few sashings and cornerstones and see if you like it. I thought it would be too busy for my quilt top, but it really pulled everything together.