CM posted this in the comments. I don’t know that it is true (I have no reason to think CM is punking us) but it would explain lots of the mystery..
This isn’t a fake image…but it’s not from 1986. It’s from 2008 (or so) on the last generation, widescreen HD Diamondvision. They recreated the message for ESPN after a game. You can see 2008 Shea mixed in with 1986 footage here:
http://www.youtube.com/watch?v=6IFL1ByLW3U
I was working at Shea the day they did it; it was after a game when most (or all) of the fans had left.