I am a visual gal. Would love to see a picture of the Sunbonnet Sue blocks you have made. What size are they?
I looked up a lot of SBS quilts, and most quilting was done to emphasize the lines on the SBS....the arm, the hat, even made ripple lines in the dress skirts. You can do swirly's, circles, wavy lines, meadering
https://www.bing.com/images/search?v...RST&ajaxhist=0 or sunbursts or little dogs and cats, flowers. Anything you can visualize and find a way to keep stitching, without cutting your thread, can be considered a quilting stitch. If you fabric is flowery, maybe trace some of the flowers.