The term "Implied Narrative" has been adopted to describe Trampier's style, a style of which I am very fond. I must admit that most every piece of D&D art that I have viewed, since becoming acquainted with Trampier's artwork, has been judged against his narrative approach.
Several months ago I mentioned the early black and white artwork of Todd Lockwood. The early Lockwood illustrations also capture a narrative ambiguity which I find compelling.
Viewing Lockwood's illustration of Orcus, I found myself asking: Is Orcus sleeping or drooling? Why is has this woman been brought to his throne? What happens next? The great strength of Tramp, and other artists like Lockwood, is not just that the scenes they depicted were filled with action, drama or suspense.
Like my favorite art, I prefer implied narrative in my role-playing games as well. To quote from Only A Game:
"Implied Narrative: this is another category of [game] narrative where, like The Sims, there really is no writer-defined narrative per se, but the stories emerge from a dynamic play environment."
No writer-defined (or Dungeon Master defined) narrative. I think this is the key (or what we imagine to be the key) to the appeal of Trampier's artwork, and the appeal of old-school gaming. The lack of agenda on the part of the Dungeon Master when it comes to what story will be told.
Like a good Dungeon Master, Tramp wasn't necessarily rooting for the good guys. Heck, we don't even know that characters in his illustrations, or the player characters in our games, are the good guys! That is up to the players themselves, or the art-viewers, to decide.
Just like the ending to their story is up to the players.