James - you have broken the custom jpg for TV Season Folders in the latest update.
UPDATE - OK, its NOT broken but in order for it to work you have to run a FULL metadata search through all of the files first ? - that doesnt make a lot of sense as it should be able to pick up the Folder.jpg immediately but instead it goes online immediately and downloads the priimary one from thetvdb - your custom one will not show up until AFTER the metadata scan has run - it never used to do that :(. The ability to FIX movie artwork is also becoming quite a necessity as themoviedb is changing primary jpg’s far too often and causing unecessarily long scan times when starting Infuse 
It does have to do a scan of the share first to find the custom artwork. I just timed it and it took about 20 seconds to recognize the new artwork. It also reverted after removing the custom artwork back to the fetched artwork in about the same time.