Add a check for images instead of icons in the main menu

[Zodiac1978]

I know this is a chicken-and-egg-problem.

2020 I asked for a rule to disallow images in the main menu:
WordPress/wporg-plugin-guidelines#71

It was closed because it wouldn't be enforceable.

Maybe adding this to the plugin check plugin could be a start to at least recommend not using images, as they are often conflicting with one of the possible color schemes.

Best practice would be to use a dashicon or a custom SVG that will use the color from the color scheme used.

If you only want to add checks stated in the guidelines, but the guidelines don't want to add them, because they are not enforceable, we will have no progress here.

What do you think?