If you want to incorporate Sashiko designs - there are several nice embroidery disks. Otherwise, if you have the patience, set a sewing machine to the triple bean stitch and use that for an outline. I've used it for simple border designs and have had quilters ask me how I got the effect. There are books for doing "straight line" designs with a walking foot which also contain how-tos for curves.
I have a pattern for making a sweatshirt quilt. I've used continuous border designs on the sleeves with the bean (triple straight) stitch. That's what one quilter at a show saw.