I'm so glad you finished this up. It came out really well. I would go for texture rather than specific quilting motifs, so I would match the thread to the section being quilted (so 3 colors: white, black & hot pink) I would echo what Tartan said, and match the bobbin thread with the top. It will save you headaches in the long run. Since the design is so linear, I see curvy filler quilting. Curls, swirls, paisleys even loops. One filler in the white, one in the black. Then go with lines of some kind in the pink. You could just echo 1/4" in from the seam on the pink.