What comes to my mind would be echo quilting around each of the circles you have on the quilt top, with each round being further out. Eg. first at 1/4", second at 1/2", third at 3/4" etc. I would draw it out on paper first to see what incremental sizes look best. Perhaps start some other circles randomly on the quilt top.
Then where the echoed-circles from one meets the other, I would stop the one series, so they would not overlap. Yet continue in the rest of the non overlapped area. Kind of like ripples on a pond, when you toss in a couple of stones, one is going to predominate, the other subside.
Clear as mud?