I just finished a self-asigned exercice to learn a bit Cycles lighting.
The idea is to take a random image (in this case http://www.istockphoto.com/stock-photo-3769413-detail-aluminum-machining.php) as an inspiration, and try to reproduce the lighting and materials conditions.
The result could be made more looking like the istockphoto image, but the main idea is to keep some lighting choice to ourself, not just copy reality.
The file was released on blendswap :
here are 2 results :
here is an HD version of the first image :