I think we need to re-classify my posting, not as another sad case of user-error, just a milder form of "User Duhhh".
The behavior I was concerned about occurs when I apply the MetroTouch skin to a page and then view it in a conventional browser. A mouse-over triggers the response which is the primary annoyance.
Later, I tried to duplicate the issue on an iPad and an Android tablet. When I press, I get useful feedback as the image button is manipulated by your code. I never noticed the downward + right shift on the mobile devices because I am right-handed and the affected area on the screen is obscured unless you make the effort to look closely.
Furthermore, I can see that such a manipulation is about the only option for a purely graphic button, there is no background or border to manipulate.
I applied the non-touch Metro skin to the affected buttons and that was an effective solution.
You might ask why I'm using a "touch" skin for most of the site optimized for larger, non-touch screens. It's because I like the way it looks. Good job by whoever did your skins!!!