I am by no means an expert, and haven't much formal training, so this critique is only a few things that I noticed, but I may be entirely wrong, so take them with a grain of salt.
Overall I really like this piece. I like the colours, and the eyes are beautifully done.
The shading is good on the contours, but the contours join together at the front of the neck suggesting that the neck isn't very long, yet the arch on the back of his neck suggests that he has a long neck. I would extend the contours downwards as a suggestion of the neck muscles, and used to give the direction of the neck.
What jumps out at me straight away as being slightly odd is the angle of the head. His head seems over-bent. His chin looks like it's touching his neck, which wouldn't be a naturally comfortable pose for him. Let him hold his head up high and proud, because he's so beautiful, he deserves to