Audley
... do you mean actual concept art or the kind of art that is incredibly brilliant and incredibly hard to get unless you have zillions of dollars?
Sorta both? Like, actual concept stuff- prep production work, lol - uhm, I've done that for the artist, ahahha.
Like, I'm looking for something more realistic, with good anatomy, a full color scheme and wide value range. Like, more muted colors with touches of bright rather than everything being shiny. Also, lots of greens and browns. Very dark, detailed work. More armor-that-can-be-made-from-real-things-in-a-apocalyptic-world rather than armor-that's-super-perfect. Most importantly, though, realistic faces, I'd suppose, no smallnose-big-eyes. Things which, even though may be too pretty for real life, could be envisioned as three-dimensionally believable.
Lines or lineless don't matter because if it's good it's good.