Exclude File Hash's from Data leak/Insider policy

Absolute long shot, but is there any way to exclude file Hashes from the attachments part of a data leak policy, we use a service for our signatures and due to the way it works the images in it keep getting picked up as part of sending external with attachment, the image name changes, but the SHA-256 stays the same.

Anyone have any idea if this is or ever will be possible?