I can see also that for new images a "message.publish" action gets recorded, but I haven't yet gotten much further in investigating how the relation between these media and text content is being established.
Just wanted to leave you with a link to the Bulk Data API documentation which might also help you further this investigation: https://developer.khoros.com/khoroscommunitydevdocs/reference/bulk-data-api#export-reference
The examples of media uploads I found in my data so far are actually avatar uploads, so they are not tied to a message id. They will all land in the user's media album though which is what explains why they are registered as a "publish" event. I agree though that it is confusing that it's a "message.publish" event and not a "media.publish" event.
