The glossy chains look nowhere near as good as the texture of the mask. Maybe try make them out of similar material or at least add some more noise.
The only other thing I'd do is taper the glowing areas so the tops and bottoms are pointed, or use some halation and bloom. Overall the lighting is a bit flat, but I'm not sure that adding more volume or particles would really help.
One thing about the model is that where the chain attaches to the head (mask? skull?) is kind of messy. Maybe use smaller chains and have them wrap around, or have some kind of rivets or something.
Overall, really cool piece. Reminds me of lore of stuff like Diablo where the big bad demon is sealed. Is there some story behind this thing?