Drupal - Migrating images and files

Thank you for Berdir's help but I noticed that I was missing some information on my drupal7_fruit migration file like the values for field_image and migration dependencies.

The working solution:

migrate_plus.migration.drupal7_image.yml

id: drupal7_image
label: Images
migration_group: drupal7
migration_tags:
  - Drupal 7
source:
  plugin: d7_file
  constants:
    source_base_path: '/var/www/username/drupal7/' # Full location of your drupal7 site
process:
  fid: fid
  filename: filename
  source_full_path:
    -
      plugin: concat
      delimiter: /
      source:
        - constants/source_base_path
        - filepath
    -
      plugin: urlencode
  uri:
    plugin: file_copy
    source:
      - '@source_full_path'
      - uri
  filemime: filemime
  status: status
  created: timestamp
  changed: timestamp
  uid: uid
destination:
  plugin: entity:file
migration_dependencies: {}

migration_plus.migration.drupal7_fruit.yml

id: drupal7_fruta
label: "Migrate Fruit Content Type"
migration_group: drupal7
migration_tags:
  - Drupal 7
source:
  plugin: d7_node
  node_type: fruit
process:
  nid: nid
  vid: vid
  langcode:
    plugin: default_value
    source: language
    default_value: und
  title: title
  uid: node_uid
  status: status
  created: created
  changed: changed
  promote: promote
  sticky: sticky
  revision_uid: revision_uid
  revision_log: log
  revision_timestamp: timestamp
  field_description: field_body
  field_image: # Image field name in Drupal 8 site
    plugin: iterator
    source: field_photo # Image field name in Drupal 7 site
    process:
      target_id: fid
      alt: alt
      title: title
      width: width
      height: height
destination:
  plugin: 'entity:node'
  default_bundle: fruit    

migration_dependencies:
  required: 
    - drupal7_image

Hope this may help anyone with the same problem in the future!

images and files are their own entity type. The node table just contains the file id, basically an entity reference.

You need a separate file migration that you need to execute first. You can create it based on the d7_file migration template.

Note: If you migrate the existing nid and vid (and fid), you need to be certain that you have no existing data with conflicting ids on your D8 site or you will get conflicts. You can leave those out then it will automatically use auto incrementing ids just like when you create content manually. But then you need to set up a migration process plugin to map the old to the new file id.