Shadows can add a lot to a photograph. They can emphasise the emotions, create surreal images, and be using a variety of ways. While strong use of shadows in colour photographs tends to be mostly used in silhouettes, it can also appear in a variety of other forms in colour photos as well. In my opinion though shadows on most powerful when used in black and white photographs.
The use of shadows, especially when photographing nudes, you can emphasise the beauty and fragility of a model's body, and add a touch of mystery, by dressing the model with shadows. Wherever there is light, there are shadows, and wherever you put an obstacle between a direct light source and a body you create shadows on the body.
You can play with different forms and patterns, with light direction and light intensity. You can create a mood with your use of shadows, suggest a story with them, or make a statement - the possibilities are endless.
Shadows of the most simple, inexpensive and effective props available to the nude photographer. By using them in this way you stimulate the viewer to look beyond the nudity of the model.