Local Episode Fanart?



I know you can drag and drop fanart for an episode in the web app but I would like to add episode fanart at the LOCAL level. For all those beautiful nature documentaries, it would be wonderful to have high res images in the background for each episode. I've tried over 2 dozen variations (not kidding) on naming schemes but nothing has worked. I've been trying to figure this out for over a year now, I would be eternally grateful for a solution to this. Can it be done in some .nfo workaround? Thanks in advance.