If you're looking for something easy to do (no free motion), you could just cross-hatch the center of the quilt at 1/2"-3/4" intervals using the pinwheels and diamonds to determine the angles. Then maybe echo quilting in the border around the entire quilt, like large concentric rectangles, perhaps at a narrower distance apart (1/4"-1/2") than the cross-hatching. At my present skill level, that's what I would do, anyway. And it would look nice, too.