It is proving that “dictation of the Holy Ghost” is a belief of the Holy Catholic Church.
Do Holy people worship dead bodies on display?
It *proves* nothing.
Anyone simply looking at that image would not have a clue what it is about without someone telling them.
Any image that is going to be instructional, especially to uneducated masses, needs to be clear enough to be understood without being *interpreted* for them by someone else.
If the message is not intuitive, then it has not been presented well enough.
In that picture, there's absolutely no way that someone could intuitively know that that was *Gregory the Great* or what he was doing except some guy was writing something.