We need more:
Adrian Smith - He's worked on Chronopia, Warhammer and most recently on Dark Legacies. You can't get grittier that Adrian:
http://www.redspirepress.com/previews.htm
Stephanie Pui-Mun Law has done some fantastic work for Green Ronin:
http://www.shadowscapes.com/
Great for fae related material.
Kalman Andrasofszky is a fantastic. His work is all over D20 Modern, Dragon and Dungeon magazines:
http://www.horhaus.com/weblogs/kalmangallery/index.html
Justin Sweet is a master. He's done a lot of concept work for the various D&D computer games out there. Check him out:
http://www.justinsweet.com/GALLERY/ILLUSTRATIONS/TNgallery1.html
Glen Angus is...(I'm running out of superlatives here...pick one) . He's done work on Magic: the Gathering as well as a bunch of illustrations for Dieties & Demigods and Unaproachable East. His Character Sheets are well worth the money:
http://www.gangus.net/workshop.htm
Jeremy Jarvis has a lot of style. Some people don't like him but I love his work. He has an excellent illustration of a Drow fighting a Moon elf in Races of Faerun and his Bladesinger prestige class illustration is wonderfully evocative. Top notch:
http://www.jeremyjarvis.com/
Jon Foster has done a ton of work with Star Wars but can easily lend his considerable talents to fantasy. A serious artist:
http://www.jonfoster.com/
Chuck Lucaks has done a bunch of work for Dungeon as well as some of the hardbound rulebooks including the Expanded Psionics Handbook and Libris Mortis among others. He has a style all his own:
http://mywebpages.comcast.net/clukacs107879MI/
I first noticed Kev Crossley in Green Ronin's Mindshadows setting. Great black and white pieces. Full of flavor and movement. One of my favorites:
http://www.kevcrossley.com/
Vinod Rams is Awesome, awesome , awesome. His illustration of the Tanarukk (orc-demon crossbreeds) in Races of Faerun is amazing. So are his Tieflings and Genasi. No website. WTF?!
Oh yeah, William O'connor rocks. A recent illustration of his that comes to mind is the Whisper Gnome in Races of Stone.
I can't get enough of Matt Wilson, Sam Wood, RK Post and the fine folks at Udon but all of these are abvious choices.
Raven Mimura is right now, my favorite fantasy artist. You might recognize this piece:
His website:
http://www.ravenmimura.com/gallery_section.php?section=1&page=1
Lastly, WAR defines 3.X D&D in my eyes. We can't get rid of him he's too good. I first noticed him in the pages of Slavers one of the last supplements to come out for Greyhawk in 2nd edition. His color work is great but his black and white illustrations are perhaps the best in the business. I think he should be used more for interiors than he is. Oh, one other thing, could someone please explain to me how it is that this man doesn't have a website?!
Who do we need less of? That's a touchy subject since it's hard to do without hurting someone's feelings. Let's just hope the art directors are the one's reading this and not the artists.
I'd get rid of Dennis Crabapple, David Martin, Steve Prescott, Baxa (ick!), Jeff Easley (double ick!), Dennis Cramer (ugh), Michael Dutton.
Wayne England is one I'm on the fence with. He has an illustration of a tome in Libris Mortis that I love, however I'm not fond of his work elsewhere. His illustrations of a dwarfs in races of faerun are aweful.
I could go on but I'll leave it there. Need less to say I'm forgetting a bunch. I think the problem WotC faces is that with time some of these artists become too expensive so they find new less expensive ones. Ultimately it's the quality of the work that dictates the price. Or so it seems.