It's not really criticism but more like suggestions and hopefully you will find this useful:
1-choose better base colours for Rukia's face and hair (green isn't the best colour for the reflection on the hair)
2- when you shade the face, choose a colour that is darker than the base and blend it with the base by adjusting the capacity of your brush (you can use blur tool as well). Also use a lighter colour than the base to add a bit of definition to the nose and lips.
3- you can always add some shading to the clothes by using the method in number 2 above
4- the eyes white can be shaded too
I have done some quick touch ups to your pic to show how the suggestions above can improve the colouring a bit \/
Good to have you on the bleach art forum and hope to see more of your work in the future