Change image of maximized button if window is maximized already.

Hi guys,

I noticed that all existing themes didn't change image button on maximized
window use always one image.

As I understood need to use window-maximized-hook... Could you please
specify a example on any existing theme how I can do this? Or maybe... Is
there theme which do this already?

I ask this because I'm not deeply familiar with rep to do it. =(

Thanks,
Vladimir