I finally produced a Photoshop'd image that I'm reasonably happy with for my version of the Call of Cthulhu scenario 'The Haunting'.
Caught in the light of a player's oil lantern and freshly daubed in red paint on the site of the ruins of the Chapel of Contemplation, the party will find:-
I'm quite happy with it, although it could be improved by some drips or similar. It does look a little artificial. Still, I think it's better than simply scanning the image from the CoC rulebook.