Mr. Maliszweski has posed a fun question over at Grognardia: what cover art "encapsulates... 'D&D' in a single image"?
Having really gotten into D&D in the Silver Age, Elmore, of course, springs first to mind, and I think I'd have to go with this one. It's from the cover not of a rule book, but one of the early Endless Quest books TSR put out way back when. In this one, Return to Brookmere, you're an elf returning to your family's ancestral home after it's been overrun by monsters. The story is fun, and mostly consists of you sneaking about, trying to find your way out after a bad cave-in nearly crushes you.
There's a lot to like in this picture. The humanoids with their horned helmets, banners and skull-topped standards, the sinister wererat on his throne, the subterranean locale, and the bar of gold caught in the decorative border.
But most of all, I really like the hero. He (She? It's appropriately androgynous for a first-person choose-your-own-adventure style protagonist) has stolen a humanoid helmet and cloak to hide the finer garb of an elf warrior, including bright mail and soft boots. As decorative as his crenelated cuffs and purple tabard might be, his notched shield and long blade certainly look all business.
But if I'm willing to follow the lead of my fellow bloggers and not limit myself to simply covers, I'll have to go with this image. Yep, that's Elmore again, and I think it was originally released as a promotional poster at Sears (buy a certain amount of TSR stuff at Sears and get this cool poster type thing). I love the stories this one tells. Does the dragon know she's down there? Is he only distracting the dragon to give her a chance to get away, or to set up a back-stab? Clearly, an attempt to steal some gold without attracting the dragon's notice has gone awry. Do our heroes have any other tricks up their sleeves?
And I love the little details: the mountainous background, the clearly functional but not historical armour, the expressive faces of everyone in the painting, including the horse. This is a great painting, and has, for quite some time, been the picture that epitomizes D&D to me, and the you-are-there feeling I've always tried to evoke in my games.
But if we're not going to limit ourselves to just D&D and the clones, I'd probably have to say that this (NSFW!) painting by Keith Parkinson comes closest to encapsulating my gaming these days.