Since it is so linear, I would probably do a wavy line down the middle of the black. Once done, if it doesn't 'feel' secure, then do something circular in the big squares. I would probably mimic this circular thing in the border. I tend to be minimalist in my quilting. I prefer to emphasize the fabric rather than the quilting. But, you can always keep adding to the quilting.

That's absolutely beautiful! I was going to suggest finding a pretty stencil for the 6" blocks but I see that has been suggested several times. :) I just love that quilt!!!

I would echo inside each shape, so as not to compete with the design or the beautiful fabrics. But then, I grind my teeth when I see a floral quilt in a book or magazine that has been quilted in a (competing) "flower motif to enhance the theme," so consider the source. :)

hugs,
charlotte

I would do a square on point or diamond in each 6" block.

I really like your colors. That is such a pretty quilt.