Demon Stone is a game put out by Stormfront Studios (which is no longer in business). It was never properly marketed so I'm not surprised at all that you haven't heard of it. The game play was pretty poopy, but the overall LOOK of the game was pretty amazing given that it was on the PS2.
Shame about the game overall result you've done a great job with the concept art work. I'd kill to have a job doing something like that haha. Are you working on any other games at the moment? Sorry with all the questions it's just game concept art is one of the things I dream of doing in the future haha