I thought I had found a bug, but it’s probably just the UI being unclear about the difference between icon and image.
To make matters worse the help text reads “Use either a Font Awesome class or URL to an image” and there is one field titled “Icon” and another titled “Image”. When I saw this I assumed I either put a font awesome class into the icon field, or I put an image url into the image path.
After trying to “debug” this for a while I finally figured that I was supposed to put a Font Awesome class or image URL into each box. Icon is for small badges image is for (not sure where this is used yet).