A trick I use to make an image feel more three dimensional (not to appear flat) is to first render the shot in one color - it doesn't matter which color, although black is a great choice. Use only the environment, material type (reflectivity), textures and composition to manipulate the effect. Follow up with more color and material choices once the lighting /environment is set.

Sketch by Jeff Michael - Dept. Industrial Design - Wentworth Institute of Technology