Get image url from model good practice?

I don't understand what you mean

in your example you have a Model which uses exactly the foreach approach

foreach($result->result() as $single) {...

and if you have a function where you know exactly that you expect only one result
than you can write something like 

PHP Code:

$result = $this->db->get();
if ($result->num_rows() == 1)
{
    $objProduct = $query->row(0, "Product_Object");
    return $objProduct;
}
return false;