I did a quick paintover to illustrate where I think you could improve.
First, let me say, there is no shame in mirroring one side of the face to ensure you have a perfectly even look. The eyes are a different shape, as is the forehead, the cheeks and the ears ( and yes I am taking into account the change due to expression ). The eyes are too far apart as well.
I don't want to hear the excuse "well it's a monster so it's supposed to look ugly". Once you make perfect face, uglyfying it is easy.