Perhaps it is just your style, but the Zexion you portray seems to be very reserved. I mean look how cute it looks, all shy and acting as if Xemnas is going to find out he was the one who stole the last cookie from the jar.
Ok, I'm no artist, but let's see what you can improve on. For starters the head size to hair volume ratio could use some work. Also the skinny neck indicates starvation. Are you feeding your Zexions well enough, Rsmv?
Comparing with the official image as referenced by the wiki, your Zexion could use some more confidence and action. Observe that Zexion's outstretched arm serves as a sort of focal point of action. Props are also good. The lexicon provides some extra character to Zexion, and the fact that its pages are midway through turning is an action focal point as well.
However, it seems your style is more geared towards emo. Try to think of some poses that the stereotypical emo tend to do. Off the top of my head, I picture Zexion with eyes closed and a hand covering a part of his stern face as if he is in deep emotional pain (lolwut Nobody) or just plain facepalming. This would make your drawing a little more exciting rather than reserved. Then again, I'm just making blind guesses as to what your style is.