I quilt and embroider. Instead of doing traditional quilting I would hand embroider. I would add flowers, butterflies, bees, balloons etc. I think it would enhance, not detract from the Sunbonnet Sues. As for thread, I frequently find bags of embroidery thread at thrift stores. There are lots of examples of embroidered Sue blocks on line. Most show the figure with arms moved or the body bent in some way but not all of them. I think adding your creativity would make it even more of a precious quilt to pass to your granddaughter.