Provide link to file option
Overrides File::buildOptionsForm
public function buildOptionsForm(&$form, &$form_state) {
$form['filemime_image'] = array(
'#title' => t('Display an icon representing the file type, instead of the MIME text (such as "image/jpeg")'),
'#type' => 'checkbox',
'#default_value' => !empty($this->options['filemime_image']),
);
parent::buildOptionsForm($form, $form_state);
}