So you have the center blocks done? If you need 16 to make the center symmetrical, I would hand quilt that last block. After that I would just machine quilt in a meander or large stipple, as Jingle suggests. It will still look great!!!
Edit: Have you machine quilted before? If not, be aware that you need to secure the quilt layers well before starting with the machine. Is the quilt thread-basted? Pin-basted?