There was a lot of great art work on 70s album covers. For the first time en masse, Rock and R&B/Soul musicians started utilizing artists to interpret their music on the cover. The trend started in the mid-late sixties with psychedelic rock bands and continued to other genres of music as well. Though, unfortunately, its often very hard to track down the name of the artists as they were often not credited.
"Innervisions", a landmark album, has amazing artwork tucked into the album and on the back cover. It took me a while to find out that the artist was Efram Wolff, who there isn't a lot of information about online. The O Jay's also had beautiful album cover art with "Ships Ahoy" which was done by James Barkley, portraying the shared struggle of black folks on the deck of a boat gazing at the stars and huddled in the belly of a ship, evoking symbolism of Africa and the slave trade. Marvin Gaye's "I want you" is not only famous for the sexy soul on the album but also for using a classic 1971 painting by Ernie Barnes called "The Sugar Shack" which depicts the early Southern juke joint hangouts where R&B and the Blues were born. The painting, labeled 'neo-mannerist' for its distortion and elongation of body proportion and space, caught Gaye's eye and he became a collector of Barnes' work. He then asked Barnes to do an adaptation for Marvin's album to show banners hanging down that represented Gaye's music. The painting was also adapted for the opening of the show "Good Times", cementing it as an iconic painting. I couldn't find any info on the cover art for Grant Green's 1970 album "Green is Beautiful" but its a lovely contour style line drawing background with unexpected shadowing of Grant's figure.