I hope this is only the first of many more!
For this update, I was able to cover everything about the unreleased game by Vigil games: Warhammer 40k Dark Millenium Oline.
Joe stated in an interview that he didn't draw that many concept arts about the game.
Most of them were done by many other talented artists at Vigil games.
As a consequence, the only pieces of art I was able to find come from Joe Madureira's Facebook page.
Except some exclusive and excellent concept arts that John Pearl at Gunfire Games kindly gave me! Thanks a lot for that John! ;)