Arthur Adams produced the "Marvel Heroes and Villains" lithograph for Dynamic Forces. We could easily peg these versions of Spider-Man, Fantastic Four, Avengers, X-Men, and their various villains in the mid 1960s era. You've got Daredevil standing next to Black Widow, that edges you in the 1970 territory. :-)
Golden drew this poster of the Marvel Universe in the 1970s. It actually may have come out around 1980 or so--Moon Knight is featured, and he wasn't popular until the late 70s with his series starting in 1980. But it's very 70s in spirit, with the All-New X-Men, Storm's classic costume, the Avengers (just love the Vision sinking into the ground), Black Bolt, Hulk, Doc Strange, Silver Surfer, and the Watcher on the left. There's a few Marvel Monsters with Ghost Rider and Man-Thing. Heck, even Ka-Zar, Luke Cage, and Captain Universe are in there.
Golden also drew this print that was featured in a 1980s Marvel Calendar. You can immediately see the difference in this post-Secret Wars era, with Spidey's black costume, Beta Ray Bill, Grey Hulk Joe Fixit, New Mutants, Archangel, and Iron Man's armor that he donned in IM #200. Note also the prominence of Daredevil and Elektra due to Frank Miller's work on the series. The Punisher, another top seller, is also in the background. Beyond the characters, the awesome sauce is the setting--the heroes in front of the Pan-Am building and crawling around the statue in front.
Alex Ross produced this cover for the Marvel Comics Encyclopedia.
This widescreen poster by David Finch, collecting all of his covers from X-Men Legacy, will be arriving in comic stores this June. Didn't read the series, but this image is stunning. Classic X-Men and New X-Men as bookends, with Sentinels, Hellfire Club, and Magneto sandwiched in-between. Nuff Said!
Update: Comments from my old MT blog...