The glow and lighting effects are beautiful here— so many shades of blue. And the use of texture is wonderfully distinctive— he's actually got a complex layering of different scale types, hair, horns, etc. They all convey very different feelings of touch, and it help make the image more immediate. The glowing crystals, lighting effects, his eyes also give him a very vibrant feel; it makes his model look flat and dead by comparison.
A/B-ing him against the model, the design differences that stand out the most are the lack of the downward-pointing horn, the fact that the beard rounds his face & joined his eyelashes, and the changes to his facial structure.
* The beard suits him well— it fits a mage perfectly. He wears it well, and it's much better than the model's interpretation. He's also the only dragon with eyelashes, and the look works there as well. The fact that the two join might make it a bit harder to use the eyelashes to convey emotion (important since he's mostly lacking pupils), but it's a minor thing.
* The changes to his facial structure are the most noticeable. The slimmer look fits really well— by comparison the model's head seemed way too wide and blocky. The lack of green overtones is also well-integrated; always seemed odd for a Blue Dragon to be greenish. The nostrils and bridge of his nose are surprisingly pronounced, and unlike the model the bridge of his nose doesn't form a triangle over/under his eyes. These last couple details are probably the thing that made him less instantly recognizable.
* The downward pointing horn always struck me as a subtle joke by Norgannon. If you think about it, that horn would effectively be a giant lawn-spike— If Malygos sets his head down, or it's driven down, he runs the risk of getting stuck to the terrain. Seemed uncomfortable— and embarrassing. So this definitely works out in his favor.