If you're referring to the cover of the album that Bob was
trying to save as the ship was sinking, it was the cover for the
Incredible String Band's The 5000 Spirits or the Layers of the
Onion.
Here's a bit more about it - hope this helps.
http://rockpopgallery.com/items/autographed-prints/the-incredible-string-band-the-5000-spirits-limited-edition-autographed-print-lep-spspisb5k1-detail.htm
Mike G