OK, so I was looking for info on this. And since I found only tidbits of what I was looking for I experimented with this file and after which I decided to post so others could find it all in one place.
To start, the Window.png file is what determines the look of your game interface (what you are looking at all the time while navigating windows.) here is what I learned...
The file has several parts, 8 to be exact, marked in red:
I have Provided a PSD file with the base Window.png file and layers defining each area for reference that you can turn on and off.
Text Prompts, (24x24)each Selected Text BG,(40x40) Selected Text Border.(48x48) Color Section.(96x48)
I hope this Helps those that are looking to edit their windows!
*Please note!*Edit: from what i found out during testing, is that the border of the "slected text border" is 4 pixels from the out side of the area to the inside, anything past the 4 pixel mark is considered the Selection window background, which is stretched to fit the area it needs to cover to the borders, so putting an image/Pattern here is not recommended as it distorts it greatly. The same holds true for the Background window area, It will distort images and patterns as well.