i.ytimg.com/vi/7kBwu8dLVsc/maxresdefault.jpg
By A Mystery Man Writer
Getting all the video thumbnails from a video
i.ytimg.com/vi/I4j4OGl_XHQ/maxresdefault.jpg
All about Thumbnail Images as ytimg maxresdefault especially in Search
thumbnails extractor
thumbnail link doesn't work in all cases - Stack Overflow