hobgadling is entirely correct about the above covers. To fill in about the rest:

Wish You Were Here - come on guys! He's making a deal with the devil. Representative of Roger's feelings about record companies. Basically in the same vein as Have a Cigar. The robotic handshake being more representative of Welcome To The Machine (and remember, that was the original album cover IIRC).

Animals - the pig is, of course, a Pig from Roger's P3DO. It represents money grubbers, usurers, and corrupt politicians. People who want to force their ways on others, etc. It's in front of the power plant to enhance the overall ugliness. Really, what is uglier than a power plant?

I remember hearing the DSotM album cover explained somewhere, but don't recall what is was all about. However, there is an obvious connection between the prism and the pyramids. Anyhow, you might also be interested to know that the cow from AHM is the as one in the Eurythmics' Sweet Dreams video.

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Isn't it sad we're insane?