Landships II

Though I'm always terribly gun-shy about posting something that may be "old news" to all of you, a search of "tank", "panzer", or "char" in the search field yields a nice spread of postcards with images of Marks, FTs, and Schneiders.  The images themselves are probably well-known, but at least you can purchase the card directly if you'd like.  Also, multiple languages supported.

http://www.ak-ansichtskarten.de/ak/