The illustrations are from (top to bottom) the 1981 D&D Basic Set (Moldvay edition; art by David S. LaForce), a 1981 Games Workshop ad (artist unknown), and the 1982 French edition of the D&D Basic Set (Moldvay edition; art by Jim Holloway). I find it fascinating that the concept of role-playing was once so alien that it had to be explained with thought balloons. And I still can’t get over how awesomely bloody the GW sketch is.
If anybody knows of similar illustrations, please let me know.
UPDATE (2/11/2016): Thanks to Kai S. and Steve Wall, I’ve added two more illustrations. The first one (fourth image down) is the book club edition cover of Dicing with Dragons (1982), with art by Victoria Poyser. The second is from Dragon Warriors: Book One (1985), and the artist is Bob Harvey (see here and here). Brilliant stuff.
2 Warps to Neptune 