Rules: Copying field from user's account to field in content type
I think you need to add some more stuff in that Rule; namely, following from your explanation, you need to:


"Create a new entity": Create a new node in an action, before the image-copying action. This new entity is a Gallery-type node.
Use the "entity_created" variable as the destination entity.


That should be enough to accomplish your goal, hope this helped some!

Appendix A: An export of such a Rule that worked.

{ "rules_196457" : {
    "LABEL" : "196457",
    "PLUGIN" : "reaction rule",
    "OWNER" : "rules",
    "REQUIRES" : [ "rules", "file_rules" ],
    "ON" : { "user_update" : [] },
    "IF" : [
      { "NOT data_is_empty" : { "data" : [ "account:field-user-image:file" ] } },
      { "NOT data_is" : {
          "data" : [ "account:field-user-image:file" ],
          "value" : [ "account-unchanged:field-user-image:file" ]
        }
      }
    ],
    "DO" : [
      { "entity_create" : {
          "USING" : {
            "type" : "node",
            "param_type" : "article",
            "param_title" : "New pic for [account:name] | [site:current-date]",
            "param_author" : [ "account" ]
          },
          "PROVIDE" : { "entity_created" : { "new_article" : "Created entity" } }
        }
      },
      { "file_rules_copy_file" : {
          "source_entity" : [ "account" ],
          "source_field" : "field_user_image",
          "destination_entity" : [ "new-article" ],
          "destination_field" : "field_image",
          "remove_source" : "0"
        }
      },
      { "drupal_message" : { "message" : "A new Article has been created with the new user\u0027s image" } }
    ]
  }
}


Appendix B: An screenshot of the Rules UI