The art is clearly a pasteup of several different layers, with no effort made to keep consistent lightning or even add shadows from one object to the other. (Just like Charm, from the same artist.)
Some examples:
Necromancer's feet (or any part of him, really) cast no shadow, despite the fact that he's holding a freaking light source twenty cm from his foot. This gives the disconnected feel to the image, and gives him a measure of "floatiness".
The zombie in Necromancer is also pasted on the floor image, and you need to look twice to realize that he's actually supposed to be bursting out of the floor. He casts no shadow on it, nor does the border of the hole cast a shadow on the zombie.
Necromancer's pose is completely disconnected to the scene. You're freaking summoning a zombie, while looking at something off screen and having a completely neutral pose. This smells heavily of recycled concept art.
Compare with the good art of Summon (from the same artist, even), for a scenic pose.
The freaking column doesn't cast a shadow either...
Apprentice seems completely off scale, and has completely different lightning than everything else in the scene.
The sky is dark in Spy, but everything else is incongrously lit by a sourceless light.
Mason should really cast a shadow. There isn't a single cast shadow in any of the four images.
This art is deeply sub-par. I wish RGG put stricter quality requirements on Dominion's artists. I'm actually tempted of dropping Jay an email.