FILE is the related List or in Attachments and you need an IMAGE
When FILE is the related List or there is a file in Attachments and you need to grab an IMAGE. The image must be in the document, not an attachment.
Navigate to Salesforce Setup > Salesforce Files > Fields to create a custom field on the Salesforce File Object.
Create a new formula text field and name the field. For this example, the field name is File Image URL.
Enter the following URL: LEFT( $Api.Enterprise_Server_URL_100, FIND(
".com", $Api.Enterprise_Server_URL_100 ) + 4)&
"sfc/servlet.shepherd/version/download/" & Id
Create a Conga Query with this syntax: SELECT
ContentDocument.LatestPublishedVersion.Image_URL_Formula__c FROM
ContentDocumentLink WHERE LinkedEntityId = '{pv0}' AND ContentDocument.FileType IN
('PNG','JPG','JPEG')
Note: If you want to filter with the title instead
of the file type, then use this field: ContentDocument.Latestpublishedversion.Title
In the button URL, add the Query: &QueryID=[FileImages]IDofQuery
In the template, the following should appear: {{TableStart:FileImages}}{{IMAGE:LATESTPUBLISHEDVERSION_FILE_IMAGE_URL}}{{TableEnd:FileImages}}