Things change faster than they should...
Greetings Ghost Fans,
Back when the Mansion was in its development stages, the changing portraits had multiple concepts in terms of how they would change. Video loops, multiple slides, etc. For the Disneyland Mansion, the concept eventually went to a simply two stage projection. One lamp would come on and the other extinguished. However, this only allowed for 2 stages. Marc Davis, who created much of the changing portrait concepts, often had many different stages, more than two in most cases. When Walt Disney World opened, its Mansion had the first 6 stage portrait, The Aging Man, or, as he is more widely known now, Master Gracey. One concept was of the Flying Dutchman portrait still seen in Disneyland's Mansion. Many of the stages were released in a 1999, Haunted Mansion 30th Anniversary lenticular. Now, seen here are all of the stages.
In addition, Dan Olson has examined the artwork and, with his vast knowledge, adds the following:
"Did you notice the depiction of "St. Elmo's Fire" in those paintings? An eerie electrical phenomenon. Glowing balls on the ends of masts and yardarms. Even in the last painting there are little white balls on the tips of a couple of them."
For more information on St. Elmo's fire, please refer to the following Wikipedia article: St. Elmo's Fire.