I play EVE online, which runs without a hitch on Vista (at least on my machine.) After noting that there was some additional lag compared to running on XP, I took a look at the compatability tab. There is an option called 'Disable Desktop Compositin…
I would guess that the concept art was created a while back in the dev cycle. This is a way to not give the look of the actual models this far before launch, while still giving us visual goodies to munch on.