Hi Zarshaan, thanks a lot for giving such a detailed explanation. I had no idea I was overwriting a special promotional image like that, and I'm sorry. All I thought I was doing was adding a brighter picture for the character's main page. Thanks for explaining that it's not a page-by-page thing, but one sourced image across multiple articles or projects... I hadn't understood that.
And I am sorry for being so vocal considering I'm just a "new user with no profile info." I'll be more careful going forward and probably just go back to lurking so I don't mess something else up. Again sorry for the confusion on my part and thanks for taking the time to message me.