LONDON (Reuters) - Graphic artist Storm Thorgerson, who designed the cover for Pink Floyd's "The Dark Side of the Moon" album and also created artwork for Led Zeppelin and Genesis in their heydays, has died aged 69 from cancer. Thorgerson was a teenage friend of Pink Floyd's founding members and became their main designer. His most famous work is the prism and rainbow stripe on the "The Dark Side of the Moon", which marked its 40th anniversary last month. It was voted the greatest album cover of all time in a poll by website musicradar.com last year. ...