Using Photoshop you can create some really interesting plays on light and shadow similar to the standard start up Mac background in OSX.
This tutorial is an intermediate tutorial and uses the pen tool, a bit of brushing and a gradient. Anyhow this is the first tutorial i've written for years, i went through the old deviantart tutes and found the ones i did when the site first started, they've all gone offline so I thought its time to start afresh
Anyhow hope this helps someone in some way. I actually use this technique in corporate work so it does have some practical use from a design point of view. Just remember to keep it subtle! (thats like my motto)