This is as vague a clue as you can get, but I found a site with greeting cards from a Northern Ireland artist (http://www.alganarts.com/greetingscards.htm), among Lenaganny and a a few other things, there is this

http://www.alganarts.com/images/Cards/SquareCards/LongStone.jpg

There are contact details (at the bottom of the page) maybe the artist can shed some light, does seem to have sketched loads of sites in N.I.