I would use a meander - something totally nondescript, but curvy. I'm not sure I would have it quilted heavily. The only reason for heavy quilting, as I understand it, is if it's going to be washed frequently. With so much white, that might be necessary, depending on how it's used.
I'd try really light violet as the thread color. Your pattern is so striking, I would not use any color that stands out. White might look too stark against the blue. Let the piecing be the star.
It's a beautiful quilt.
bkay