iOS Notification Question - Firebase

Quick question in regards to the Notification Service.

Does the Google Firebase service which HA uses to send out mobile notifications have the ability to ingest an image from a local path and send it along with the notification without the need to provide a public link or use the nabu casa service?

-OR-

Must you provide a publicly accessible URL to your HA install (or use the nabu casa service) for the image to be viewable in the notification?

My notification code includes:

  - entity_id: camera.pool_equipment_profile000_mainstream
    data:
      filename: " /config/www/tmp/snapshot_pool_equip.jpg"
    action: camera.snapshot
  - action: notify.mobile_app_new_iphone
    data:
      title: Looks Like The Pool Guy's Here
      message: Check to make sure he turned the water off!
      data:
        attachment:
        content-type: jpeg
        url: /local/tmp/snapshot_pool_equip.jpg