I don't know how to more emphatically tell you that Debord was such a Marxist his many of his theses from Society of the Spectacle literally were copying/detourning Marx lines. His "plagiarism is necessary" thing is something he lived up to when writing the book. Like three quarters of things in the book are other writers words twisted into what Debord wants to talk about. The Lettrists/Situationists were literally building on what came before.
The spectacle is not a collection of images; it is a social relation between people that is mediated by images.