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.
When you say ‘Episode’, you probably mean a series, right?
naming schema for series is covered here:
https://support.plex.tv/hc/en-us/articles/200220717-Local-Media-Assets-TV-Shows
You need to stick to it (including the folder structure!), otherwise your ‘local assets’ (posters, theme music, subtitles) are not found by Plex.
Btw: if you mean with “fanart” the background picture and not the episode preview thumb - sorry, not possible. The background is only valid for the whole series.
Thank you trumpy81 and OttoKerner for your quick responses! trumpy81, I have tried all of that many times over 
I really was looking for episode fanart/background/backdrop/art. Yes, OttoKerner, I was looking for background picture and not the episode preview thumb. It is a real bummer, I figured there must be a way since you can add one via uploading or drag and drop in the web app. Thank you guys so much for your clarification, looks like I will open a feature request.
