Really beautiful piece! I really like the composition and the colors usage! You did an amazing job! And a big highlight for me is the rendering on the crystal it is superb!
The only thing I could suggest to improve this piece, would be to have utilized some AA ( Anti Aliasing ), I think it would have made the piece just a little better. That being said I can also understand why you may have not utilized it, as the pallet didn't always have a good color for it, depending on the values (though I for sure think that some could have been applied to the middle as they were quite a lot of "yellow-ish" hues!
Regardless, an amazing piece! I really like it!