My crits:
- Dragons eyes are starring blankly into space instead of towards the knight. The dragon's eye brows could be slanted down a bit as well to add some emotion.
- Theres too much saturation in the scene overall. In real life there are small water particles and dust particles in the air that cause things to lose their saturation as they go farther into the background. If your 3D editor has a fog setting this could be used to get the effect, otherwise throw it in photoshop and tone down the background having places in the extreme background almost completely desaturated. A gaussian blur in the background would help as well, to bring focus into the foreground and the main scene.
- The composition overall is pretty basic in terms of placement. You've centred the two characters right in the middle of the scene. Its almost always best to use the Rule of Thirds (look it up on wikipedia). Position the dragon to the farther right, the knight also far right past the middle point of the image, and add some more scenery to the left, to move the viewer's eye through the scene.
- The knight's head is a little round IMO. But thats a matter of modelling skill.
- Reflections in the water would add some more believability.
- In terms of the motion blur, it looks a little cheesy. If you are going to use it, go all out, blurring parts of the dragon's head and the knight's arms as well.
- But most of all the character's poses are pretty awkward and uncomfortable. I understand you're going for a sense of motion but its not working to me in this scene. Id recommend either having the knight mid-air as if he were jumping towards the dragon, with his sword in both hands showing him about to make the final slice. Or have the knight putting his weight on his back leg, his back arched away from the dragon holding his sword in front of his face awaiting the large blast of fire about to his him.
Thats my opinion. The idea is there, it just needs some work. Here is a very quick mock-up of some of the ideas I've mentioned, (obviously I couldn't change the character poses and whatnot).
As you can see simple things like the background desaturation and blur already make a huge difference in where the eyes focus on the scene.