It's obvious that Microsoft would not release such an option soon.
If you need to hoover over a picture that should be used as a button, then you can do it yourself with a little trick.
1. Put a button over the picture (or any other control) with the same size.
2. Delete text of the button.
3. Set its color to "transparent" in order to see the picture below.
4. Set the button's border color the same as the background and the size of the border to 5 px (you can play with this size for receiving the desired effect).
5. Set HoverBorderColor to transparent.
In this way you'll "take" 5 px from every side of the picture (if you're willing to sacrifice them for the sake of this effect), but when hover over the picture it will appear with its full size making the protruding effect.