absolutely.... Yes.
hopefully you have the artwork with the movie/video ? The using the 'information' command with the movie in question in focus, choose 'art', then pick poster or fanart.... migrate to the bottom of the list, pick 'browse', 'item folder' then the artwork.
Alternatively you might want to clear out your thumbs, rescan all your sources locally. Local art should be chosen before web art.
Alternatively you might use the add-on 'Artwork Downloader', turn off downloads, and enable local art only in settings.
As an addendum, naming conventions must be followed.
Artwork (wiki)