The original DDG has tons of great illos. Here's one by David LaForce that totally blew my mind when I was a kid.
Back in the day I was baffled by those bad guys. Who the hell are they? At one point I considered that they might be an NPC party from some parallel Prime Material Plane where they play a Teenage Mutant Ninja Turtle/Palladium Fantasy hybrid game. Eventually I settled on the idea that the tiger-headed guy was a rakshasa, the bird dude was a kenku and the boar-head guy was an orcish cleric. Together they formed a sort of dark mirror anti-PC party, a pro-active multi-racial group of badguys to oppose all those mixed parties of goody-goody dwarves, elves, and humans.