Hi,
The options images are not loaded on the product page since there is no need to normally.
So, as I said, you first need to load them. You can do that with a MySQL query on the hikashop_file table like that:
$db = JFactory::getDBO();
$db->setQuery('SELECT * FROM #__hikashop_file WHERE file_ref_id IN (XXX, YYY, ZZZ) AND file_type=\'product\'');
$images = $db->loadObjectList();
And XXX, YYY and ZZZ are the ids of your products or variants (if you have options with variants, then it's the ids of the variants that you want to set in the query).
Then, to display the image with the index $k in the array $images, you can do like that:
$image_options = array('default' => true,'forcesize'=>$this->config->get('image_force_size',true),'scale'=>$this->config->get('image_scale_mode','inside'));
$img = $this->image->getThumbnail($images[$k]->file_path, array('width' => $width, 'height' => $height), $image_options);
if(@$img->success) {
echo '<img title="'.$this->escape($images[$k]->file_description).'" alt="'.$this->escape($images[$k]->file_name).'" src="'.$img->url.'"/>';
}