I have all the artbooks that came with the collectors editions and have trawled the conceptart.org postings regularly - there's definitely plenty of concept art that gets into the actual game! I was positively delighted to find the flamingo-house-boat-things in Elona after I'd seen them in the concept art! Seriously, exactly the same.
A lot of the time the armour doesn't translate that well, though...

I think that's more a technical limitation or to save on the effort of making multiple armour models (just reskinning)... That's particularly true for the male mesmer.

Sorry, guys, your armour is 90% kind of ugly and the same. D: But the male mesmer armour concept art looks so good. T_T