Add Drupal image template suggestions by bundle and field.

THEME.theme.php

<?php

/**
 * Implements hook_theme_suggestions_HOOK_alter().
 */
function THEME_theme_suggestions_image_alter(&$suggestions, $variables) {
  
  // Get the directory and filename.
  // Need to use dir and filename to form the URI, since trying to load the file by filename alone
  // will skip files that might have been uploaded with the same name as another and had "_0" added to the end.
  $path = parse_url($variables['uri'], PHP_URL_PATH);
  $path = explode('/', $path);
  end($path);
  $filename_key = key($path);
  $dir = $path[$filename_key - 1];
  $filename = end($path);
  
  // Load the files and get the node they're used on.
  // This is a bit of a cheat since we're assuming it's only on one node.
  /* @var \Drupal\file\FileInterface[] $files */
  $files = \Drupal::entityTypeManager()->getStorage('file')->loadByProperties(['uri' => 'public://' . $dir . '/' . $filename]);
  if ($files) {
    $usage = \Drupal::service('file.usage')->listUsage(reset($files));
    $usage = reset($usage);
    $nid = key(reset($usage));
    $node = \Drupal::entityTypeManager()->getStorage('node')->load($nid);
    
    // Add suggestions for each image field on the node.
    $fields = $node->getFieldDefinitions();
    foreach ($fields as $field) {
      if ($field->getType() == 'image') {
        $suggestions[] = 'image__' . $node->bundle() . '__' . $field->getName();
      }
    }
  }
}