I just did a large I-spy quilt for my kids to have at the family cottage. I stitched in the ditch around all the squares. If your batting allows larger areas to go un-quilted, (some say up to a certain size) you could just go around the 4patch. Or tie the quilt with a tie at each corner of the 4-patch, or along the sashing. You could do different floss colors on the ties for additional I-spy fun.