Ability to render `icon` on unchecked radios and checkboxes

[hacknug]

I'm working on two different sites (designed by different folks) and for both I had to implement this kind of radio input:

Due to icon only being applied to :checked elements, I couldn't rely on it to style the input. Given it automatically escapes the SVG code and let's us take advantage of iconColor, it would be great if we could use it to add a bg-image to all radios regardless of their state.