I would use a variegated thread in the black areas (perhaps even in the cats) You would be surprised what colors are available now. Black in the bobbin.
Now as to planning the quilting. You can put press and seal or plastic over the image and design without touching the fabric. It sometimes helps to know how it would look finished before you begin. Also it gives you a memory hand to eye experience that helps to keep you focused. If you need to trace quilting templets to use the golden paper to follow as you quilt. I can't remember the name just now, but most on line stores sell it. You sew the design and tear it away.
Another option would be to use a built in embroidery design from your machine in the main body area and then the echo stitching with a stipple in the background black area.
Last edited by RedGarnet222; 03-31-2019 at 01:34 PM.