Nice, i like proportions. Although picture looks good it could be even better. Here are some tips (only my hole opinion):
1. Work in higher resolution (4000px x 4000px, 300 DPI). I think this is the reason i can see pixels on your lineart (i.e. crown) :D After image is done just decrease the it's size.
2. Make your lineart better: use different width of lines. You need to have pen with sensitivity for it.
3. In my opinion, your art is a bit too curvy. For example, hand which is holding a cube has weird fingers. Looks like it misses bones. Also we can see too curvy lines on trousers folds around the knees. If it is your style, ignore this.
4. You used only one type of shadows. Picture misses at least hardshadows. Again, maybe it's your style. But i still think hardshadows will make your art looks even better.
5. Use combination of hard and soft shadows (You have used only hard). I highly recommend you to spend 15-30 minutes by reading these tutorials:
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http://fc05.deviantart.net/fs9/f/2006/011/c/9/060105_SoftCellShading.png
http://caydett.deviantart.com/art/Cel-Shading-Tutorial-270935090
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Here is also very useful video tutorial about shading but not exactly what i am talking about (https://www.youtube.com/watch?v=qtLZCfwZVcw). Although it has 40 minutes, believe me that it will worth this time.
PS: Thank you for sharing your arts. Keep it up!