What sort of pen did you use to add in the washed out tones? I really like the sketchy style of it.
I use a selection of Leteraset Promarkers. Use a warm grey #1 or #2 for the lightest tones, and a #5 or #6 for darker areas. You need a quick stroke to keep the ink light. Sometimes I go over the Letereset pens with a graphite stick to give a bit of texture but that only works if the paper has a bit of texture for the graphite to grab onto.Picking warm or cool grays can change the feel of the picture so experiment.
Thanks will give it a go. The style of your sketches are really nice. I prefer working with ink, seems to be more free than just pencil.