Art and illustration are fundamental to a good roleplaying experience, equal to the rules themselves and cooperative participants. And if you're like, mostly ignorant of the basics of drawing and painting, art is the most mysterious.
Hardly any piece of D&D art can claim to be more prototypical of D&D than Trampier's AD&D Player's Handbook cover. I don't even need to show it to you, as it is no doubt a fixture of your imagination, as it is of mine.
Many of his pieces from the Monster Manual are also unforgettable to me, after long hours in the summers of the late '80s spent flipping through that book on family fishing trips, particularly the Rakshasa, which I tried to name a cat after, but had to add a glottal stop to, because of pretentiousness.
I learned about his passing here.