I like the idea of a simple sashing, maybe a soft green, pink or violet, that doesn't overwhelm the flowers, which should be the stars. Complicated quilting patterns are great for so many things, but I think in this case the flowers should take center stage, not the block designs. I wouldn't want thick bands of color, no matter what shape, to come between the flowers. Pretend each one is a framed picture and they're all arranged together on a wall, maybe.