With the name field of your images, it will add a title on the image.
If you want a tool tip on it using the name of the image, you can edit the file administrator/components/com_hikashop/helpers/image.php and change the line:
$html = '<a class="hikashop_image_small_link" rel="{handler: \'iframe\', size: {x: '.$this->width.', y: '.$this->height.'}}" href="'.$this->uploadFolder_url.$path.'" onclick="SqueezeBox.fromElement(this,{parse: \'rel\'});return false;" target="_blank" onmouseover="return hikashopChangeImage(\''.$addpopup.'\',\''.$this->uploadFolder_url_thumb.'\',\''.$this->thumbnail_x.'\',\''.$this->thumbnail_y.'\',this);" '.$optionslink.'>'.$html.'</a>';
to:
$html = '<a title="'.$alt.'" class="hikashop_image_small_link" rel="{handler: \'iframe\', size: {x: '.$this->width.', y: '.$this->height.'}}" href="'.$this->uploadFolder_url.$path.'" onclick="SqueezeBox.fromElement(this,{parse: \'rel\'});return false;" target="_blank" onmouseover="return hikashopChangeImage(\''.$addpopup.'\',\''.$this->uploadFolder_url_thumb.'\',\''.$this->thumbnail_x.'\',\''.$this->thumbnail_y.'\',this);" '.$optionslink.'>'.$html.'</a>';