Well.....

The anatomy is a bit long. You just really need to get your proportions a bit better.
The arms lack a bit of definition and your feet really need a bit of work.

The overall character design is a bit boring, The mask and clothing are the biggest reason that it is dull. They lack any sort of folds or wrinkles to make them interesting.

You have similar problems with the pose. It lacks dynamics. But at least I can tell you tried. You should have stuck her left arm out instead of her right since that would have added some flow to the picture.

I want to say that the lighting is bad, but the problem is that there is no lighting. You have some gradients going, but they are weak, and besides that, gradients are a bad way to shade. You need to plug in a light and get some real shadow cast on parts of the body, as well as some proper highlights. If you mix this with some good clothing folds, the costume can come out looking pretty decent.

I'm not going to go in to the background, I think Ash covered that well enough.

ok

id say practice backgrounds, nobody likes gradients, they dont look nice any way you use em, next your anatomy, the legs look good, but you might wanna practice the arms they seem a bit long, they normally reach just below the waist, not at the knees, and finally shading, there barely is any, clothing is hard to shade, but anything is better than nothing, gives us something to look at to tell you to improve on, and gives the picture some depth, instead of it looking really flat, basically you just need practice and youll be fine, so you know what to do, find some tutorials and practice