PLUS PLUS PLUS.HOBBY CRAFT have single fold cards. deckle edged. C6 size. 50. yes 50 cards with envelopes several coloures. for just under £5.00, these are ideal for creating those wonderfull machine embroidered cards.

I would suggest that you actually sew the desing ont some satin type fabric and then cut it out to fit onto the front of the card, use a baste stitch to hold it in place leave about 1/4 inch free fabric past the sewing and then frey it.
you could then place the words seasons greetings inside the card in the stitched block. just a suggestion, annie in the Uk