I have long been puzzled by a couple of shots in the final flashback of OUATITW.Harmonica's brother is about to be hanged, and the montage gives us a shot/reverse shot sequence depicting the exchange between the brother and Frank. Suddenly, we see close-ups of members of Frank's gang (one is eating a piece of fruit). We do not know who these men are, we have never even seen them before (except in long shot), and they will not show up again. They really have nothing to do with the plot, but provide a certain ambience that (perhaps) only on-lookers can supply.The sudden introduction of the faces of the gang members is striking and, as I said, somewhat hard to account for. Recently, however, watching The Quiet Man (on AMC) I saw something very similar occur in THAT film's one flashback scene. John Wayne is back in his corner, while the man he has killed lies motionless on the mat. We cut back and forth between Wayne and the prone body. Suddenly we get closeups of onlookers: perhaps a trainer, other ring personnel; we don't really know because, again, these are people who are never introduced and never appear again.Perhaps Ford did this in other places, but I was struck by the fact the Leone not only copied this technique, he used it, as Ford had done, in a flashback.
Seriously doubt it's a direct reference, but I watched "Doctor Zhivago" again today and I noticed a crane shot pretty much identical to one in OUATITW. When Zhivago is captured by the Red Partisans and they ride off into the forest, the camera pans up slowly as the music reaches a climax to reveal a simply huge forest. Reminded me of the crane shot revealing Flagstone in OUATITW. I'm not saying it's a reference, but I found it interesting that the two shots in question were practically identical.