The corners I personally would go with the purple marbled(?) print already in the quilt. Then, I would use the outer green fabric you have laid out and the lighter purple. That will make the darker purple print just jump, at the same time tying all your fabrics together. I am not sure I would put the peach/pink or the blue or the dark green print around the quilt at all. My opinion only. And to add, I think you have done a great job with the color and fabrics on this one. Very nice!!