[Komet]

As far as I know (please correct me if I'm wrong!) there is no way to make Kodi re-read a poster/fanart when it has been cached. The API however provides a method to update the image urls (VideoLibrary.SetMovieDetails thumbnail, fanart). From my point of view this is pretty much useless because Kodi will still show the old images.
So it would be very nice if the API would provide a method to "really" update the poster/fanart of movies and tv shows.