I think your quilt is perfect as is too... unless of course, you need it to be bigger. I would avoid floral also, I think it would spoil the geometric appearance. Do you possibly have a blue similar, but maybe just a bit darker for the binding? If not, I think I like your idea of using the blue you have anyway.
if you have lots of scraps left, maybe you could do a smallish light border and then another border with rectangles separated by your light fabric, then another small light border and your binding.