That is so cute! I love the bright colors. I'd be tempted to use a variegated thread in primary colors and quilt the triangles either 1/4" inside each triangle, or if you are comfortable doing FMQ, you could go corner to corner on the triangles arching a bit towards the center then back to the other corner. Another thought, you could do straight or squiggly lines that meet in the center and spread out towards the edge, like rays of the sun. FYI - squiggly lines are very forgiving! :)