At that same 1990 centennial conference one had the pleasure of sitting at a downtown Providence cafe with four or so other attendees, one of whom was Gahan Wilson. Warm and unassuming in person, chatting about several graphical and prose projects he had underway at the time.
And AHA! On the second night of the 3-day event, at a Providence movie house, was the world premiere of...!!!
IMDB mistakenly gives the release date as 1989. But it was actually there at that conference in August 1990.