javootoo.com is a useful resource if you are interested in alternative Swing Look and Feels. Every time I look, another one seems to have been linked - though most seems to be fairly subtle variations.
It's a few years since I've had much chance to work on a Swing application; I do mostly J2EE work now. But back then I was given responsibility for the GUI on a project where the analyst had heard somewhere that a gentle yellow background was more motivating for users, or something. Picking up the Windows colour settings wasn't the default behaviour at that point, and it was before 'themes' were introduced, so it required me to extend WindowsLookAndFeel and learn about some of the internals of the L&F system to be able to specify colours. For amusement I set it up so on my own workstation the application would start with a random set of colours, which got some strange looks when we were testing.
curious