The thing is, both of those were memorable poster images or main-title graphics (what we in the 60s, prompted by having a father in the business, referred to as "Saul Bass titles") -- so successful at their purpose that they instantly summon up the movie, and as such they seem (to me) to be bridging the time gap, and thus less of an outlier. Go back into the 40s, and that kind of "invent one image to recall it all" mindset wasn't so much a priority.
And in that context, I can see that the Barry Lyndon one does also presents a unique graphic, it's just that the movie itself hasn't become immortal like the others. (I too was impressed -- how did they make it look like he lost his leg, from all angles, when CGI hasn't been invented yet? -- but not truly involved.)
Truly, it's not that advanced, or I wouldn't be able to do it! I'll leave image capture aside because it may depend on your OS or perhaps need a special app (the capacity is now built into the newest Mac systems, if you know the key combinations). But image searches are truly easy, at least with Google (the only one I've tried):
After any search, I see a row of options across the top of my browser window (All / Videos / Images / etc.). If I choose "Images," up in the window for typing one's search is a small icon of a camera. Click on that, and I get a new search window that prompts me to either give it the URL of an image I want to identify, or upload an image I have saved on my computer. After I've done one of those actions, I get a long list of pages that contain that image.
I was clued into this by a helpful friend in his 20s -- I hadn't immediately understood about it myself. Now I use image search all the time to track down unidentified pictures. So I've ventured onto this sidebar as a way of paying my own belated education forward.