Lynn Nicoletti sells designs for Embroidered Envelopes from her website lynnenicoletti.com. On the site you will also discover a brief article illustrated by an image embroidered postcard that was mailed in 1915 from a British soldier, in France, to his sister in England.
Lynn Nicoletti also offers cross stitch designs with hidden images in them. In her design diaries you can witness how the designs developed. Finally what cross stitch site would be complete with out some Free Charts to download.
Those embroidered postcards are lovely – but very very fragile now. I used to be a volunteer in part of the Australian War memorial in Canberra, which has quite a lovely collection – and you can ask to see them if you’re organised enough to make arrangements with the textiles curators in advance.