In the Form Builder default photo tags allow you to link a photo with fields in the form such as the Date, Client Name, or Location. 

To add tags you need to add the object name of the question that you are tagging to the photo into the tags box, this is entered in square brackets separated by a space and a comma. 

Eg[formText_1], [formDate_1] these items being the object name of the fields in the form.

See image below;