I do see that in your artworks there is very little yellow. Although I've got to say you have this one done quite nicely. If there is something that could improve this a little, in my opinion, you could add a little more 'sparkle' to the dress (reminds me of the fluttershy dress you did). Yes, this is a sin and it's supposed to be dark and/or gloomy, but a little sparkle wouldn't hurt. After all, this is gold and diamond and shiny blings we're talking about. Don't you agree?
One more thing. Absolutely love the texture of the diamonds on her right shoulder!