Well after three different attempts at borders, I finished piecing the top of my commissioned quilt. These colors were a challenge to work with, but I'm pleased with the results. I used the circle quilt tutorial here, but did use a fusible web for the outer edges of the circle to prevent fraying (which adds a lot of work cutting each circle by hand, rather than with a rotary cutter), and I chose to use a blanket stitch. I tried the striped border on my quilt that you see in the tutorial, but with these fabrics, it was just too loud :). I opted for a thin strip of stripes instead.
Now I've got to decide how to quilt it!