Oxymandias, do you mean this chariot?
http://demonwinner.free.fr/uk/1989/golden_demon_winner.php?categorie=8#1st
I vividly recall this model as well and was in awe, although I can't say I changed my painting style because of it. However, I'd be curious as to whether or not Mike Butcher was influenced by it at all... it looks a bit like his style, and he went on to win a number of "Best Painted" and "Army Appearance" awards in North America for years and years with various Nurgle armies. His stuff did influence a number of gamers and converting enthusiasts, I'm sure of it.
KruleBear, I actually own that exact book by Shepherd Paine! I picked it up on a whim at my local hobby shop, which I was picking up a pack of birch seed leaves. Great stuff, although I think I'll leave him out of the list, for the same reason I'll leave Miguel Jimenez out. They don't work much in 28 / 32 mm scale, and nothing with a gaming background. The line between "gaming miniatures" and "figure / military modelling" is getting so blurred these days, but I think we all have a rough idea what is in our "genre", and what isn't. If there was a model / work of art within our genre that we could point to, where we could say, "This is when someone successfully drew influence from outside our hobby, and introduced it to the miniature art community, which led to a revolution in painting", then that's the project I'd like to add to the list.
On that note, there's a really nice annual publication called, "Spectrum", which features "The Best in Contemporary Fantastic Art". Every year, tons of artists submit work to a panel of guest judges (top artists like Brom, Dave Dorman, etc., along with Art Directors from publishers like WotC, Marvel Comics, LucasArts, etc.), and a few get selected to be featured in the next book. A few years back, for the first time that I know of, a miniature was selected to go into the book. It was a Cryx warjack painted by Alison McVey, and last year, a sculpt by Allan Carrasso(sp?) was included in Spectrum 19. I thought those were bold steps from our genre into the outside art world. We've been drawing influence from 2d art, computer games, comics, movies, etc, for eons... could it be that the reverse will slowly become the norm? If so, then that humble warjack could be considered a truly influencial game changer.