What I want to figure out how to change are the less-customizable graphic components of windows, such as the actual bitmap images buried within the system that dictate how things are going to appear on the screen. Here are a few of the ones I am looking to figure out how to change:

The texturing of the title bar of the window. I've seen customization that goes deeper than just changing the color.

The border that surrounds active applications on the taskbar.
(Couldn't get a picture for this one)
The overall appearance of the start menu, primarily just the graphical layout of the entire thing.
That's pretty much everything I want to know about, I've found out where the images are located for all of the other graphical components on my own.