At the end of the movie, just after Cheyenne dies, Harmonica rises her head and look at the sky. The camera moves up and before focusing on the train arrival you can notice that Harmonicas hat perfectly overlaps with the mountain just behind. I think that Harmonicas specific head move is not an accident. I m sure that Leone asked Bronson to rise his head to that precise position because of the mountain (such a move is not at all natural). I guess that Leone want us to know that West legends died but didn't disappear at all. They stay in the landscape of the west like easter island statues (moais). They are legends of the west forever carved in the stone like in Mount Rushmore. Maybe Leone thought that west legends deserved that like great US presidents.
I don't know about Leone's intent with the mountain here (I need to re-watch that part, or at least see a still photo), but I think Leone did plan ALL movements, like Mortimer tugging at his ear at the end of FDM.