• If all related files are images and all are required - create a Standard Relationship
• If not all related files are images and filtering is required - create a SOQL Relationship.

SOQL Examples:

Parent Object Files: Copy Type = Table or Row
SELECT ContentDocument.id, ContentDocument.FileType FROM ContentDocumentLink WHERE LinkedEntityId = '<<Parent_Object_Id>>' AND ContentDocument.FileType IN ('PNG','JPG','JPEG')

Child Object Files (Table > Row): Copy Type = Table
Select id, name, (SELECT ContentDocument.id, ContentDocument.FileType FROM ContentDocumentLinks WHERE ContentDocument.FileType IN ('PNG','JPG','JPEG')) FROM Child_Object__c WHERE Parent_Object__c = '<<Parent_Object_Id>>'

** Locate the correct corresponding Child_Object__c & Parent_Object__c API names for the specific environment.

2. <<Tag>> the DocGen Template with the desired tags and behavior.

** Append ‘__image’ to the ContentDocumentid Tag.

Dynamic Image: https://help.nintex.com/en-US/docgensf/Templates/DynamicImagesInTemplates.htm