Vin Diesel continues to play to his fans by releasing another piece of concept art from Riddick.  On his Facebook page, Diesel says that the fight to get the film an R-rating has indirectly led to an extensive pre-production phase.  I'm hoping that the film hits production soon because if Diesel keeps posting this concept art, he may inadvertently spoil his own movie.  You'll understand what I mean if you click through to see the whole concept art and read the tiny description in the lower right-hand corner.

Hit the jump to check out the full image but beware a possible spoiler.

Via Vin Diesel's Facebook page.

As you'll see in the lower-right hand corner, the title "The Last Stand of Riddick" is written in the corner.  I'll let you suss out what that could possibly mean in terms of the plot or if it's just an off-handed title that doesn't give away anything.