Wow, once again you've come up with the goods. Thank you, ori. Those screens look fantastic. That second last one looks like a painting, beautiful.
I think they are genuine screenshots. The only thing I would question is the rockfaces in the second last one, they look gorgeous. I think they all look a bit soft and glossy and concept-artish because they are magazine scans? A few of them look a bit grainy, like in a magazine.
And hooray, there are indeed black people.
One thing I'm really liking is that many of the screens look like realistic locations, not just randomly generated vegetation scattered everywhere which is the impression I was getting from how the devs described how they built the world.
I don't think they're concept art. The view models of the Mac 10 and machete are the same as the ones in the other gameplay shots and I don't think I've ever seen concept art that has first person gun models. I think the "concept art" look comes from overly compressed jpegs. Or maybe they're scans, I can't really tell.