how to create template suggestion for image like image--NODE-TYPE--VIEW-MODE
In the hook_theme_suggestions_HOOK_alter the $variables contain only informations about the theme of entity in this case theme image:
From documentation:

array $variables: An array of variables passed to the theme hook. Note that this hook is invoked before any preprocessing.

if you look at image_theme you can find all variables passed uri, title ...
So to access node related info you can use route params like the following.
/**
 * Implements hook_theme_suggestions_HOOK_alter().
 */
function THEME_theme_suggestions_image_alter(array &amp;$suggestions, array $variables) {
  $node = \Drupal::routeMatch()-&gt;getParameter('node');
  $suggestions [] = &quot;image__&quot; . $node-&gt;bundle();
}

Note: you can't access to View mode in this hook because it's not in the $variables and also the current view mode is not stored in the node object
Take a look at this issue Make the current view mode available on the node object