I've thought about quilting designs and feathers do come to mind. I don't know why but there is something about them that I have never totally liked.
Stars are an obvious choice but maybe too obvious. I don't think flowers will do, that would be in total contrast to the design of the quilt.
I have thought of suns. A circle with points radiating out in the feathered star areas. It ties in with the stars and it has the element of the points. It would add a circular shape to all the straight lines of the design but wouldn't be a total departure from it.