Check out this thread first.
So, there`s a ghostly face in the 'Resting on all four feet' room at Shinra Manor.
It just shows that one of the team developers had the intention to implement some mysterious, unexplained and deceived bits into the game. Perhaps, they expect you to regard thier subtly serect plans as probably nonsense under normal circumstances. Funnily enough, this ghost thing (especially the Aeris / Zack ghosts) brings some relevance to the story.
Of course, they have done like this to the other Final Fantasy games for some traditional reason.
P.S Sorry I don`t have a picture of the ghost to show, I tried taking a picture off a camera but it doesn`t have high quality.