Update: i got it with bit of PHP within tagcontent_tmpl.php:
defined('_JEXEC') or die('Restricted access');
$images = json_decode($article->images);
$pictVar = ($tag->type == 'intro') ? 'image_intro' : 'image_fulltext';
And then for image call:
<php if(!empty($images->$pictVar)){ ?>
<img src="<?php echo acymailing_rootURI().$images->$pictVar; ?>" />
<?php } ?>
It looks like there is no real tag to get images into tagcontent template.
Thanks again fro great and quick support.