I think your pigs are beautiful without the embellishment; a suggestion of pig is more effective than details with those nice batiks. A curly tail is the only addition I would consider, and your idea of cording would be great. Couch it in place if it would catch on things in use, leave it 3D if the quilt will be a wall hanging. You could also use fuzzy yarn, baby yarn, and the like, mixing and matching to the different batiks used. Each end of the tail could go through the fabric to the backside, using a large eye needle as in tying a quilt, to avoid ends fraying or having to be knotted. Or how about a tiny strip of pig-matching fabric glued on with permanent fabric glue, and couched or zigzagged in place, if desired, for added security.