This is the sister topic to my Toolbar options (http://www.windows7taskforce.com/view/72)
Have a color picker in the explorer window. This will alow us to chose the over all theme of the toolbar, and status box thats on the bottom. This will work great with people who want to customize and organize their items such as the libraries feature. People can label their music green, movies blue, documents red and pictues orange or what ever they like. There can even be an option for the color to match the window color.
but what ever you do, dont go the windows live way. We already had a OS that was cartoonish (a great one, but the UI wasnt that great) keep it glossy
Now this is not that huge of deal, but just a small thought.