I want an icon to come up when a box is selected

I've searched the community but can't seem to find my answer. 

We need an icon to pop up when a checkbox is selected. I found this website but it's not really working and I'm using the following formula but that's not working either. Help!

QuickBase Support Center - Icon Urls 16x16

If([Requires Supervision]=true,"<img src=https://images.quickbase.com/si/16/221-point_red.png>")