Are you referring to the full resolution one?:
https://img.youtube.com/vi/<insert-youtube-video-id-here>/maxresdefault.jpg
I don’t believe you can get ‘multiple’ images of HQ because the one you have is the one.
Check the following answer out for more information on the URLs: How do I get a YouTube video thumbnail from the YouTube API?
For live videos use
https://img.youtube.com/vi/<insert-youtube-video-id-here>/maxresdefault_live.jpg– cornips