When someone shares the creation of an image, for instance with this activity :

{
  "@context": [
    "https://www.w3.org/ns/activitystreams",
    {"vcard": "http://www.w3.org/2006/vcard/ns#"}
  ],
  "summary": "Sally created a note",
  "type": "Create",
  "actor": {
    "type": ["Person", "vcard:Individual"],
    "id": "http://sally.example.org",
    "name": "Sally Smith",
    "vcard:given-name": "Sally",
    "vcard:family-name": "Smith"
  },
  "object": {
    "type": "Image",
    "name": "A picture of my cat",
    "url": "http://example.org/img/cat.png"
  },
}

It doesn't show up in Pleroma.