When I saw the thread title and before even seeing the poll options, my answer was Abbey Road. I don't even own Abbey Road (I'm not much of a Beatles fan) and yet I know the cover very well. The cover image is that well known, and when you see parody covers or parody images that take ideas from that cover you know where those ideas came from.
I own three versions of Dark Side of the Moon and that cover wasn't the first or even the second to come to mind when I saw the thread title. The prism from DSotM is more of an icon for the band Pink Floyd than the album. When you put a sticker on your car of the Pink Floyd prism you're more represting the band than the album. Same for the skull image from "Steal Your Face" is more of a representation of the band Grateful Dead than a specific album.