How I Finally got thumbnails to work

So when you browse the Movies folder, do you see Folder.jpg representing the (500) Days of Summer folder, or do you only see (500) Days of Summer.mkv represented by Folder.jpg when you click through into the (500) Days of Summer folder? In other word are the jpgs working only for video files, or for folders as well?

If its that latter then you have the same experience as me. You’ll find that, if you put a second video into any of those folders, that Folder.jpg is use to represent both.