Your quilt is spectacular. I believe an ambitious quilting design would really detract from the quilt, and I'm sorry to say I think that includes gold metallic thread with an exception. If it were me, I'd quilt along the sashing SITD with the same color thread on top as the sashing. Then I'd take each quarter circle and do echo quilting of the circle in the same color as the fabric. You could do fancier asian-themed quilting in the borders or circles and x's through them. In my humble opinion, adding a complex quilting design to that quilt will ruin the pattern. At most, in addition to what I've mentioned, I might add two or three straight lines equal distance and coming from the middle of the circle in each quarter, and that could be done as a straight line quilting with gold metallic, but stop at the edge of the circle or maybe go around the very outside of the circle with metallic. Check that last part out on your sample.
The quilt is outstanding. Congratulations. I think you could win a ribbon on it if you used the right quilting design.