Your art style is wonderful, I love the expression that Sakura is wearing, and the way that she is holding herself seems like something that the real Sakura would do. Your background skills are FREAKING amazing i must say... [pointers for me?]
Hmm... A few critical mistakes that i must point out though are...
1. Her head is slightly lopsided, make a circle and you can see that her head kind of leans toward the left.
2. Her waist should be slightly more curved, the legs are fine...
If you look at a woman's figure, you can see that the waist is slightly curved. I know that Sakura is FLAT, but her hips should be a little bumpy.
3. Her right hand, the one that is slightly showing should be longer. Not the arm, but the hand itself. Make the fingers a little lower down and make sure that you can see her knuckles.
Other than that you really did do a good job! Pointers for BG for me plleease!