I think each application needs 2 icons, one is when the appication is not active, the second is when the application is running...

take the luma QQ in Mac's dock as an example, the penguin's eye is closed when the LumaQQ is not running, the penguin's eye is open when the LumaQQ is running....or take a look of Adium in the Mac, the Duck's eye open and closed.........

That's very cool