Full Use Case:
I have checkbox field on my Salesforce record that is either marked True or False. Rather than merging the value of the field as True or False on my generated document, I would like to merge the actual checkbox image showing as checked or unchecked. How can I do that?
You can conditionally merge images based on the checkbox values. You should create two images: 1st with the checkbox checked, 2nd checkbox unchecked, and then have a formula field that display either 1st or 2nd image depending if the actual checkbox is checked in Salesforce or not. You can review this conditional merge section article for more detail on this feature as well as this article for how to create and merge images onto your template.