Can I change the taskbar to a single image?

Hi, iv'e looked through sevenforums for quite some time now looking for an explanation (as well as the rest of the internet).
To explain, I'm creating a custom theme for windows 7... A simple steampunk styled theme... And I'm trying to edit the .msstyles file to show the taskbar as a full image (my current test is a simple wood sample, 40 pixels high, a few hundred long), but problem the problem is I can't seem to find the file to edit, I manually searched and found resource 1010 under IMAGE is the top few pixels of the taskbar... So I replaced it, but it makes no difference?
(I know the system works, as I already replaced the "Show Desktop" (Aero peek) button...

And now the question.
How does the fitting system work on windows 7 themes? if I create an image the width of the screen resolution minus 17 pixels for the aero peek button, will that work properly?

Thanks in advance.

P.S. I use:
ResHack (Resource Hacker)
Paint.NET
Windows 7 Home Premium SP1
screen resolution (on my test computer): 1366X768

Thanks, I'll try that later...

As for the image used, is there any way for me to use a single image without it being distorted to fit the screen? I don't intend to distribute the theme, and i know the resolutions of the screens I'll be using it on, so will using images the width of my screens (take 17 pixels for the aero peek button) prevent distortion?

Thanks in advance