How to access all images uri in node's field in custom module?
You can try this code: 

$img_urls = array();
foreach ($node-&gt;field_image as $item) {
  if ($item-&gt;entity) {
    $img_urls[] = $item-&gt;entity-&gt;url();
  }
}


Then all field_image image urls available in $img_urls variable.