A lot of us probably already know this, but for those who may not and are interested, much of this art is the work of a company called Hipgnosis. They did tons of work in the music industry over the years, and they're still at it, although not to the extent they once were. There are some great books out on the company and its art. Might be worth a look.
A personal note for you younger folks: I'm not trying to be weird here, but
please keep this sort of thing alive. Downloads are one thing, but there is nothing like holding something in your hand, thinking about it, having it to always go back to and remember.
http://en.wikipedia.org/wiki/Hipgnosis
Lloyd (Sorry to the OP rugerpc for the sermon and the hijack.)