If you are making the 8 point "stack n whack" you will need 8 repeats of the fabric. I recently found a Kona floral with an 18 inch repeat and we were able to us the other side of the length also. What you need is 8 identical pieces of material. Take your time in the shop and lay it out, see if you can use the "backside" without too much waste.
Anything in the fabric could be the focal point of a star. I once saw the bees hidden in the fabric become the center of the star. It was gorgeous.