I don't get good stitches hand quilting through seams, so that directs my choices for hand quilting designs. You said you've only outline quilted until now; have you tried stitching through seams yet? You might want to try that before deciding on a design for this quilt.
I think I would SITD the individual stars to make them stand out, same for around the center shape in each block. I might outline quilt those wider strips, and then stitch down the middle of the narrower ones. You could do something curvy in the border. My reasoning is, accentuate the piecing and avoid seams. On the other hand, if you don't have a problem quilting through seams, you could do just about anything, as you could if machine quilting this beautiful quilt.