There is an exhibition in London about Ray Lowry, who designed the 'London Calling' album cover.
There is an audio slideshow about it, narrated by the Clash's road manager:
http://news.bbc.co.uk/1/hi/entertainment/8741797.stm
Info about the gallery is here, even if you're not planning a trip to London.
http://www.ideageneration.co.uk/generationgallery.php