I looked it up, and its episode #17, which was from 12-1-71!
Here is the introduction from the narrator:
H. P. Lovecraft - known to the aficionados of the occult, demonology, witchcraft as a master story-teller - is responsible for our first selection in this museum of the frequently morbid. You connoisseurs of the black arts, you'll probably recognize it. It's a painting that tells the story of a young artist who recruits his models from odd places, and the models are very odd indeed. The painters name is Pickman, and the title is 'Pickman's model', and where else would you see a story like this except in the night gallery."
