How To Get The Full Thumbnail Set of Any YouTube Video: YouTube Thumbnail Generator | Online Video Publishing | Scoop.it

YouTube Thumbnail Generator is a thumbnail generator that automatically grabs YouTube generated thumbnails from videos in just one click.

You supply the URL of the YouTube video and YTG immediately provides you with the set of three thumbnails available for the specified video, just like the owner of that video sees in his account.

The service is free and it does work as advertised: 

http://youtubethumbnailgenerator.blogspot.com/