Hi arnask,
You can edit a listing view, in HikaShop > Display > Views, for example the view: "Product / listing_img.php".
And instead of:
echo $this->image->display(@$this->row->file_path,false,$this->escape($this->row->file_name), '' , '' , $this->image->main_thumbnail_x, $this->image->main_thumbnail_y);
Put the code to show many pictures, try to use the "show_block_img" Layout in the view "Product / show.php":
$this->row = & $this->element;
$this->setLayout('show_block_img');
echo $this->loadTemplate();