I love how you start off your sketches from a dark purplely sketch color maybe? Byzantium? Dark magenta? Orchid? Old Lavander? Mulberry? I dunno... ( my perception in colors are pretty weak)

But I really love how it's done.

I can see that you're using a round brush because I can still see your brush strokes :) or probably you're using multiple brush shapes atleast it gets the job done.

I like the composition, it's really simple and it really shows what you want everyone to see, no distractions, no complex background, just one mean badass chick with a sword.

I'm not saying complex background is bad, it's just that, our eyes aren't built to see too much information crammed in one illustration.