I love this quilt, the center really pops! Try quilting circles in the center to continue the infinity effect, starting very small in the center and cork screw out getting larger and larger as you reach the edge. It could be a continuous line of quilting. For the next square i would stitch in the ditch around each color in the diamond, and continue to the next square. The dark color I would use a swirl pattern for movement.
Good luck, whatever you do, it will be spectacular!