I am unsure about the z-offset for pause, arrows, etc, so for now I am just picking an offset of 10.
I separated the pause graphic into its own class, which should allow for more customization via scripts, etc. That way if your not happy with four images and a simple animation, you can easily create a script to change it without having to modify the Window class. I also included adjustable speed for the animation. I will commit soon, once it is fully integrated into the WindowX class.