Hi! I LOVE the concept of giving the robot a tattoo as well. Fits perfectly with the driver; making the robot truly belong to her, rather than appear as just a prop. They make me want to learn more about who they are and what type of world they're from.
I also love the coloring technique, which I think is why the overall image appears a bit plain to me. I'd love to see how it'll differ if more substance was added around the woman and her machine. I think it'll give it a much stronger impact, and add even more character to the subjects already depicted.
My favourite in your gallery so far, I think the composition of this piece is what grabbed me, the slightly offset main focus is balanced nicely by the fact the main elements are leaning to the other side of the page. The girl and the mech create a really eye grabbing silhouette, and the designs on the mech and indeed the woman leave the viewer in no doubt as to what is going on. Lovely use of opposing colours in the teal and pink flesh tones, instantly lifts her off the dark shape of the mech.
The background has just enough detail and design flair not to detract, but not to feel unfinished either. The only thing I feel could be improved is the pencil marks in the top right, which detract from the scale of the main elements, almost as if they were small, sat on a page of paper. Having said that, the extra lines and eye direction prompts they provide really help the image. Lastly, i love how you've incorporated your watermark/signature, nicely added to balance with the picture rather than being an after thought. All in all, a wonderful piece portraying a subject I find hugely appealing.