First off, I think you are a great artist who deserves more recognition. Your style is well-defined and quite beautiful. There are some general things you might be able to improve upon, but that's not what this critique is for.
In regards to this sketch, it is a sketch of my favorite mane 6 character, so I'm a tad biased. I love the way everything flows together, and the bold strokes set the mood of the piece quite well (I'm assuming this is discorded Rarity).
I say the originality is lacking only because you have a very similar piece in your galley ( fav.me/d603vbk ), but this may just be a result of your very well defined style.
The technique I expounded upon above. It supports the vision and is a huge part of the impact.
The overall impact is one of exceptional art. I love this sketch, and be sure that it is now one of my favorites!