I started with a very basic 3D blocking to choose the design and the composition. I did a lot of pass before choosing this design but I still not entirely convinced...
I made a line drawing on top of it. Then I painted :) I used some photo texture to add some details but a huge part was paint over. I also changed the composition a little bit to have something more open. I also changed the design a bit from the line version.
And at the end I struggled for 1 hours just to choose the color of the girl and the robot, and I still not happy with this but.. anyway. I need to move on.