This sketch of the gnome with his lantern and cricket was an offshoot of some product design I worked on for a collectibles client. I'll use it as a basis for a demo using Painter and Photoshop.
The scene will be warmly lit by the gnome's firefly lantern and the sky will provide a cool backlight. One look at my portfolio and you can see I like the drama generated by playing warm and cool light off one another.
I start by scanning the drawing into Photoshop as a 300 dpi grayscale image. Using the grayscale setting eliminates a lot of unnecessary information and gives a better scan image to work with. Be aware that a lot of shading on a sketch will block your view of layers below later on.