When creating or editing a badge, there are text fields for both “Icon” and “Image”. However, both use the same help description: Use either a Font Awesome class or URL to an image.
As an admin, I ask:
This is a bit confusing as it stands now. 
PS: Maybe a link to the current (well, out-dated) available FA icon classes would help admins know what to type here, too.
I agree, the UI does not explain what the difference is between “Icon” and “Image”.
But if I would have to venture a guess, an icon simply means the tiny image, and the image means when you look at the badge’s page you get this fancy image … but I would have to look at the source to know what the difference is for sure.
As for the PS
Unfortunately, I haven’t managed to get links to appear properly in the description fields on the settings page, but if you’re looking for FA icon classes then look no further than http://fontawesome.io/icons/
Yes, familiar with that page as we it’s an upstream component of our own software. Unfortunately, Discourse is using a very old version from Nov 5, 2013, when many 150 of the current icons listed weren’t yet included. Update is rumored to be coming someday soon. 
“Very” old? I’ve told you a million times to stop exaggerating…
Fair enough. Updated to show the Nov 5, 2013 release date.
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).
It’s used on the user card, what you get when you click or tap your avatar or @username here.
Ok, I see where it’s used now.
Thanks for the clarification.
I still can’t understand what is what - may someone elaborate, please?
The “Image” field creates a badge image that will show up using the “User Card Badge” preference option. This badge image will show up on the lower-right hand corner of the user card if selected (as far as I can tell, not frequently used).
The “Icon” field is what shows up for the badge everywhere else.
I’m hoping to create a new badge called “staff” and have each staff member have that badge.
I have an image I’d like to use for the badge.
But I can’t just upload that image to have it used? It needs to be on the web somewhere with a URL to it that I then attach to the badge setting in discourse?