Try this on some scraps, use different kinds of yarns, multiple strands of threads, braidings, etc. I have seen beautiful effects using narrow ribbon too.
Use a zig zag or the more open type of decorative stitches on your machine. You may find that on a single layer of fabric that you will need a stabilizer to eliminate puckering. Heavily starching the fabric first, may eliminate the need for a stabilizer.
A couching foot makes the process easier, but a zig zag foot with a grooze in the bottom of it will work too. There is also a couching foot made to use while FMQ
You can couch on yardage and make beautiful fabric for a unique backing, or cut it up into quilt blocks.
Couched bias strips, with a decorative stitch makes beautiful vines and stems. Experiment, have fun, and please show us your results