Using a delimiter field set to display on your list and substitutions you could display whatever you like based off that fields value. Example as follows.
[cb:if cb_myrank="1"]
<img src="[cb:config param="live_site" /]/images/1.png" />
[/cb:if]
The above would display the image 1.png from inside your image folder assuming the value of cb_myrank is 1. This would be placed inside a delimiter field then placed directly on your userlist. More on substitutions can be found at the below tutorial.
www.allmysocials.com/tutorials/item/233-substitution-usage