For me, although I am not aware of any D&D work he may have done (or even if he has done any at all), he has done a lot of artwork for Wizards... and that would be Anson Maddocks (I hope I am spelling his name correctly).
He was the guy that did some of the most beautiful work in Magic: The Gathering with such pieces as the Cyclopean Tomb, the Hurloon Minotaur and the Spinal Villain. Heck, the artwork for the land ISLAND was (in my humble opinion) crappy until Anson did some for the Ice Age set.
It would be my (wet) dream to write a monster book for D&D and have Anson do all of the artwork for it... ah....