I use the serpentine stitch also. One lady in our guild quilts all her quilts with the serpentine stitch on the diagonal, one way using her walking foot.
You can also free-motion quilt the serpentine stitch. Place 2 hands on the fabric and move your hands in gentle curves....S shapes...think of a snake. (the non-poisonous ones
) See the example on the blue section of the table runner I quilted. Don't worry if the lines are not spaced the same, just have fun!