All of his movies are heavy on regional details, with a focus on some of the same kind of Southern decay Faulkner-isms that Steve Niles jocks from time to time but if anything, there's something more genuine and lived-in--less a genre exercise for Green--about Green's update on Southern/Small-Town Gothic attitudes, which makes sense as Green was born in Arkansas and attended film school in North Carolina. In many ways, the collaboration might be ideal as I think Green will give a more thoughtful representation of small town insularity than Niles, while Niles' will retain the more immediate, simplified horror element to the whole thing; these guys can bounce off one another well.
Take a look at the severely slept-on Undertow which is part genre exercise pastiche--Night of the Hunter meets The Goonies--and part extended, rambling mood-piece with more than one chase scene thrown in for good measure and I think you'll get a sense of what Steve Niles by way of David Gordon Green movie might feel and look like. Snow Angels too, has points as horrifying and scary as any horror movie and he handles tension and suspense skillfully.
Green also has a really identifiable visual style--credit his director of photography Tim Orr for this too--that's part beautiful and ready to be mounted on your wall and part shaky and ready to fall apart but still kinda pretty and in that sense, is a lot like Greg Ruth's scratchy Rembrandt work in the original comic.
Here are the trailers for all of Green's other movies, which gives you a good sense of his style. Just remember, all trailers make movies look terrible and so, the actual movies are way better:
George Washington (2000)
All the Real Girls (2003)
Snow Angels (2007)