I have a readonly label field containing an image url from an external CDN which is populated programatically. You can see the link url in the content admin, but I'd like it to show the actual image as a thunbnail so the admin user can see it. What's the easiest way to achieve this? The image url shouldn't be editable. I was hoping there might be a way to easily include some javascript that would trigger on load and create the necessary HTML to render the thumbnail, or a guide on how to create a custom label that contains an image thumbnail as well?

Built in preview button with an appropriate template would work, but was hoping for something better so that it was visible at a glance.