This tip covers how to easily download the placeholder image from a Youtube video page.
Youtube video pages generally have a placeholder image that is displayed when the video is not being played. This image is easy to download.
Suppose a video has the following link:
https://www.youtube.com/watch?v=ABCDEFGHIJK
The standard definition placeholder image is then retrievable from :
https://i.ytimg.com/vi/ABCDEFGHIJK/sddefault.jpg
Some videos also have a 1200px x 720px image retrievable from :
https://i.ytimg.com/vi/ABCDEFGHIJK/maxresdefault.jpg
You should replace ABCDEFGHIJK with the video id of your page.