To a person above who asked: yes, they're being used in-game - most of them, anywyas, not sure about all. I know because I recognize them. But they don't really look this kickass.
To the entire anet concept art team: your drawings make me want to rebuy Nightfall so this time, I can get the Collector's Edition, and get the artbook. I havn't bought a CE yet, so ... yeah. The work here is pretty crazy, especially the monsters ... some of them look stunning.
All in all, I just got 25 minutes less sleep thanks to you [because I practically ran through the drawings ... and after losing sleep to GW anyways! Stupid Wintersday], but in a sense I wish it was 2 hours. I'll probably look at them again. And maybe even again and again.
Some amazing stuff here.