I like a narrower - 1.5 inch finished of the white in your quilt and then an outside border. It like the piano key border. You could have corner blocks of the pinwheels in the 4 corners.
I also like finding a larger print that has the colors of the pinwheels in for something different.
Whatever you decide, use a color that is already in the pinwheels vs adding a new color in there.