I joined a Facebook artist playing card group last fall. One of the people with whom I have exchanged in the group is Elsa Bouman. Elsa lives only about two miles from me and we meet up on occasion at a local commons area to create. We decided to do a collage postcard exchange and here are four of our results. We collaged both sides of the postcard partially. Then sent the unfinished card to the other. It was our task to finish the two sided postcard and return mail it to the "owner."
Not only is there the challenge of creating and then finishing postcards but we had to somehow disguise the addresses for return mailing. It has all worked out marvelously. I especially like that the post office adds to the collage. Note in the first one that there is a cancellation mark and also a white strip of paper added.