YES!!! Simon, thank you!!!!
To illustrate the comments of nick, and the exemples given from mike's book, I have electronically added some shadows on your painting (center), with a light coming from the front right side (on the left), or from the left from side of the soldier (on the right), to show you how you can give more volume effect to the body, the face, the hair, the boots, the hands, the cuffs, ... by adding not only shadows, but also highlights, depending on the direction of the light source, very important in painting a flat. It is up to you to choose where you wish to position the light source, keeping in mind that higlights and shadows must be compatible with the light direction, and if you paint several characters on a diorama or a serie, they should all have the same light source !
Good painting !
