Folder Images Reverting

[doomedtx]

I hope you don't mind me tagging on to this older post. I'm having the same issue with a "Home Movies and Photos" type of Library. It's a collection of downloaded videos, home content, miscellaneous stuff that's appropriately called "Misc." The main Library image I created has remained fixed so far, but the images I created for sub folders like the Strong Bad image below have been replaced by automatically-generated images from videos inside the subfolder. Is there a way to keep a folder inside a library from regenerating its image?
Here's what I uploaded:

Here's what I got after a week or so (Yes we watch TGS along with Strong Bad):


EDIT: Is "Lock this item to prevent future changes" what I should use, or is the folder.jpg inside the folder the best option?