In themselves, these stills evidence a fairly deliberate widescreen composition and cinematography. Still #1 to me captures the distinctive aesthetic sensibility of the film... it is at first glance the kind of vista landscape shot we associate with the New Hollywood Western/road movie, but it's actually a composition exploiting foreground and the diagonal. Shot #2 is perhaps a textbook rule-of-thirds illustration.
Beyond the formal traits, the shots exemplify three facets of the theme. Glenn gets at the crux of the theme when he notes the "lyrical clash between classic Western genre traits and 20th century progress." Like many of the 70s American films, Thunderbolt and Lightfood combines genre and allegory; in this instance, the genre film seems sandwiched in between and exposition (a preacher who turns out to be a criminal) and resolution (a schoolhouse preserved as a hollow marker of History) with weighty allegorical dimensions. In the above stills, however, we get the bare genre elements with larger meaning: the car (which Peter so well diagnoses), the male buddy-couple, and the gun. The thematic project of the film seems to be to take each of these and repurpose it, infuse it with irony.
The cynic in me thinks the film actually says less about violence, masculinity, and mobility in American life than it conspicuously shows that it is saying something about these things. Or perhaps, it is sincere in its ironic critique, but that the critique is so close to other films (McCabe and Mrs. Miller, Butch Cassidy and the Sundance Kid, $, Jeremiah Johnson, etc.) that it's hard for me to take it as something other than second-order seriousness.
It's particularly worth pointing out the gender politics of the film. This is the sort of film that would be (and perhaps was) a prime target of a certain era of feminist (Molly Haskell) and gay/lesbian (Vito Russo) criticism. My first inclination would be to move beyond the contemporaneous gender critiques, but in sum I think they're spot on: there's a misogyny and homophobia that hides behind the half-ironic pose of critique: the narration allows us to know that these anti-heros are flawed (because of homophobia and misogyny) while not ever putting the spectator in empathy with, say, the women of the film. Or else, these elements are written off as the generic part of the film, while the "real" auteur film hiding beneath is about more high-minded truths. I bring this up in part because the contradiction so pervades the film (the almost-gay kiss, the drag, the prostitutes, the youth making out) and in part because it gets to the genre-auteur contradictions of the New Hollywood.