Interesting https://www.newser.com/story/342432/mystery-of-stick-man-on-zeppelin-cover-is-solved.html
Frank Borman (recently deceased astronuat) was inserted into the cover art of Led Zepplin 2. https://www.cheatsheet.com/entertainment/led-zeppelin-ii-figures-album-cover.html/
I'm not an expert on Heavy Metal but I've got to believe Led Zeppelin, Jimi Hendrix & Black Sabbath are the godfathers of that genre. I think that Zeppelin & Hendrix were really more Blues based than Sabbath was. Ken Burns' documentary about Rock and Roll is very informative.