To satisfy my craving for 60's psychedelic, I just bought the poster on the left on Ebay for $5. The one on the right is by Steve Harrington.

UPDATE: The poster arrived in a half-crushed tube that I happened to find behind the trash can next to the garage. Did the UPS guy really think that was my back door? Slightly distressed, I pulled the poster out of the tube only to discover it was literally a computer printout on some photo paper, and definitely not a high enough res to be printing as a poster! I e-mailed my disappointment to the seller and he told me that it is a digital print, not a computer printout. What? is there a difference?
Then he refunded my money.