You normally associate great concept art with the act of building a world and its characters. You know, singleplayer stuff. But a shooter's multiplayer maps still need to be designed and dreamt up, and in cases like this the art can be just as stunning.
The pieces you're about to see are by Michael Pedro, an artist at Certain Affinity, a small studio that lends a quiet, helping hand on the multiplayer side of some of the biggest games around. The latest of which was Halo 4.
You can see more of Michael's art at his personal site and CGHub page.