Plugin to show an image in selected posts?

Hi!
I’m interested in a plugin that in some way can add an image (a badge) to the posts I choose, with a new number each time. I’m thinking that maybe there’s a plugin that lets me enter a number as a Custom Field and then displays that in a badge (something like this).
Does anyone know of a plugin that could do something like that, or something else that could make this easy?
If it’s unclear what I mean, please just ask and I’ll try to explain better!