By my reckoning, the Tom Moldvay Basic set uses about 9 pages worth of graphics (art, maps, etc.), NOT including charts. The Cook/Marsh expert set uses about 7 pages. That's out of 64 full pages, including the cover leaf.
Personally, I've always felt the Expert set felt a bit sparse in the art department and while some pages were positively inspiring as a kid (mainly Willingham's pieces), others felt...well, lacking. Do I really need a picture of a narwhale or a water termite? I'm not sure....
So, I'm going to shoot for at least 8 pages of interior art. I've already got a rough sketch of the cover (call it a "working sketch"), and at least a couple artists (maybe even four) lined up, I'll probably be soliciting anyone who's interested in contributing to the thing. Not that I'll PAY people anything, of course...but then I'm not looking for anything super-fantastic, either (about on par with the original B/X rule books; i.e. small black&white line drawings).
'Course people who contribute will retain all rights to their own art, and (if I use their piece) will definitely get a free copy when the thing is finally printed up.
Anyway...let me finish the other 58 pages first...39 down and 19 to go!