Mock: Cover Art Progression - Xenomorph

This is the initial sketch of Xenomorph from which I worked from.
I already really like the effect of having it as a plain line sketch on a blank canvas, however I feel as though it's not particularly eye drawing despite the harsh contrast of the white and black.
To make it more appealing, I decided to work into it using sketchy lines and an oil brush preset to give it a sense of incomplete design, and that it was taken directly from the original designer's sketch book.

The first thing I did was work into it with basic highlights and shadows so that I could get a sense of shape and what would catch light where. I worked roughly with an oil brush preset so that I could get blended yet sketchy effect.

Repeating the same process as above, I worked more into the sketch. I altered the transparency of the sketch so that I could get a more accurate definition with the painting.

This is the finished piece. To work into it more, I used more sketch lines on a low transparency to make it look more sketchy than painted. I also altered the paint more by working over it with an air brush set to a low opacity. This meant I could work on top of it evenly without it being over powering and masking the blending of the oil brush. 

I am very happy with the outcome as it keeps it's sketch look but with the refinement of smooth blending transitions to give it that three dimensional appeal.