Custom Resource Bars, help.

[FrozdY]

Hey, I was wondering how I would go about making something like this , where the resource bar, is more customize-able, than just a square.

Would I be able to make just a PNG, and then link the bar to that, or how does it even work?

You might think: "You already made it, stupid..." No, that was just an example I threw together in After Effects...