Chronology of iconic 1960's covers

I believe the most notable designs were for Beatles, Pink Floyd and the peice (as discussed previously) by Andy Warhole for The Velvet Underground. 

They were both known for their involvement in the Psychedelia scene of the 1960's when Hippie culture was at its height following the social phenomenon of The Summer of love 1967. The stylistic conventions of Psychedelia design is evident in their work.

1966: Beatles Revovler by Klaus Voorman 

I think there is a imaginative, sort of fuzzyness and unknowing quality about this. The use of line is  surreal and abstract, and the combined use of illustrative and added photographic elements makes it feel a bit hap-hazard. It's like a mix of real and the imagined in one place.

1968: Pink Floyd A Saucerful of Secrets Hipgosis

Dream like quality, visually busy and crowded and displays grand displays of nature (solar system). Other elements are quite obscure and difficult to seduce what they actually are. Texturally, it is warped and wobbly, a sense of chaos and uncertainty. 

1967 The Beatles Sgt Peppers Lonely Hearts Club band by Peter Blake and Jann Hamworth (based on a sketch by McCartney)

Featuring cultural icons standing with the member's of the Beatles, the group shot is surreal because the other figures are super-imposed and it is not of a real group photo shoot. This similarly brings us back to the idea of the imagined or of fantasy. 

1969: Pink Floyd Ummagumma by Hipgosis

Notably for it its illusionary use of Droste effect which is a picture within a picture, within a picture, one that might would expect when under the influence of Hallucinogens. Gives a sense of unease because of the picture repeating indefinitely, it kind of reminds me of looking at the hundreds of reflections of yourself in a mirror house.

Finally I conclude, the most iconic piece of 1960's (in my opinion) is The Beatles Sgt Peppers Club