The purpose of the concept art is to save money and plan out the production at low cost. So, what is the point of spending a few K on fancy computer equipments to do the same thing that can be done with less than a few bucks?(pencil and paper) Even including a decent scanner and a dozen cups of good coffee, it would not even come close in cost. It just does not makes sense to spend more to save money, not to me anyway.
Anyway, here is a quick sketch done in Photoshop.(As you can see, it would be much cheaper doing it with pencil on paper instead.)