If you have a lot of video content stored on your PC then the default thumbnails can leave folders looking disorganised and make sorting through your movies and TV shows more difficult. With a simple hack, you can set the thumbnails for each video yourself to show the official DVD cover, movie poster or any other standard-sized image.
Oddly enough, the best application for the job is Apple's iTunes. Import the video from wherever it is on your hard drive, right-click on the automatically generated thumbnail and choose Get info. Switch to the Artwork tab and you can add any image you like here, such as the DVD or Blu-ray cover of the movie. iTunes will update the metadata registered with the file and you'll find that you're left with a more uniform set of thumbnails the next time you take a look at the videos in File Explorer.
Depending on how your media library is set up, you might need to tweak the settings in iTunes to make sure you're working on the original file and not a copy that the program has created. Open up the Preferences option from the main menu and switch to the Advanced tab to check. You can if you wish remove the video from your library afterwards, though make sure you don't delete the actual file when prompted.