I love them!!! It is a great way to use up scraps :D:D:D
Some fabric cards I have done the piecing and glued them down, so the stitching didn't tear the card stock, I then elongated a blanket stitch and went around the edges to finish them.
Embroidery designs are fun to incorporate on them too.
If you are not mailing them as "postcards" You can get even more creative and mail them in manilla envelopes :D:D:D