I think users will try to set up any regular square (or rectangular) image as a Start button icon, but Classic Shell shows it cropped severely. It took me a few tries before I came into the forum and figured out that it needs to be in a 1:3 ratio format for all the states.
What I propose is that Classic Shell check the aspect ratio of the user's selected image and, if
Code:
width != (height/3)
assume that the user just wants to use a regular image as a button and show that as-as without trying to show different states.
This way people can put their own display picture as their Start button icon if they want, without having to open it up in an image editor and repeating it three times.