This is one of several thoughts/suggestions regarding the upcoming fifth edition of Dungeons & Dragons (5e). Relevant news items: nytimes and wizards.
I don’t know anything about the history between TSR/WotC/Hasbro and artists, but judging by what I’m seeing in a lot of D&D products I have to conclude that you’ve driven the good artists to hate you. So the first piece of advice is that you should stop doing that. Also:
No more interior art.
Keep the maps; those are good, but other interior art does not help anything.
It’s not that art is bad, per se. Certain types of art, in particular, would be great. Portraits of (in)famous NPCs and locations, renderings of certain spell effects, historically significant battle scenes, and so forth. They should not, however, be in the campaign setting book or regional sourcebooks, and especially not in adventures.
Instead, art should be on a dvd, sold alongside but not bundled with the printed material. In the name of whatever you hold sacred, don’t bundle it. Why? Because you obviously won’t have a whole dvd’s-worth of images to go with each sourcebook… and I will not pay $10 on top of the base product cost for 5 digitized watercolors that look like a 5-year old might have just tossed a couple buckets of colored water at the wall. And because —if it’s good— some people who don’t even play D&D will be interested in the art. You’ll make up the cost of producing these dvds by charging no more than $20 and making sure we’re getting more than our money’s worth. Rule of thumb: if it looks like fingerpainting, I’m not going to buy it… ‘cuz I can do fingerpainting, myself.
As far as watercolor that a 5-year old couldn’t do, very little of what I’ve seen in D&D books, since the beginning of D&D, has been as good as http://bcduncan.deviantart.com/gallery/. And no; I’ve never even met her, but she’s an amazing artist. Your art director(s) should spend a couple lunches every week, if they don’t already, browsing deviantart and other art communities. I’m sure many of the artists would be willing, or even eager, to be featured in a collection of art and role-playing materials in exchange for a fair price.