On a prior post you were right that in "file mode" in XBMC, you need a folder.jpg for the thumbnail to show up.
My movies are all in a separate folder. (> 2,500 films)
The request I have is whether a code could be written to go back over the movie.nfos already done and add a folder.jpg to the movies that don't have one (that's the majority of my movies). All it would be helpful if MC could go over and simple delete all files in a folder except the movie, then a rescan could be done.