This piece look really nice~ The shading and shadows you applied looks very digital art-esque which really adds a beautiful touch to the artwork. Anatomy-wise, everything seems perfectly fine. The only thing I could really point out is the size of her shoulders is just too small.
Her hair on the other hand looks wonderful. I really enjoy the length, the way it drapes over her and the planet she's sitting upon. The dress she wears looks really nice however I believe it would have been nice to be more detailed? Perhaps it may not be the design of your commissioner, but I believe it would have been more eye-catching if she had more complex designs along her sleeves or more so on the obi~ Speaking of the obi, the flower design is really good but I would have liked to see more of it. Same goes with the matching hair piece. Continuing on with her kimono, the ruffles could have been better? More fluff to them? (Poor choice of word but I hope you get the idea) And especially on the sleeves. However, the sleeves themselves look really amazing with their folds.
Now with the background, the sepia gradient fits very well. In my opinion, it would have looked really if the planets and moon had more shading and details to them. Not really much I could say about it. Originality-wise, I've seen this type of picture many times but that's only if you aiming to be original. It's a fantastic piece overall~ :3c