Rows of serpentine stitch can really look cute on a quilt. The serpentine stitch on my machine looks like a zig zag stitch except it has 3 stitches in each zig zag. When I increase the stitch length it makes the serpentine stitch.
Angela Walters has YouTube videos on FMQing the continuous curve or orange peel design that makes a good pattern for use in squares also.