Ok, this is how I did it and it works like a charm in 4.0.13. The following code first checks to see if a manufacturers image is available. If so, the image is shown as a link. I also created a language file called {$lng.lbl_click_more_manuf_products} which basically say "Click above image to see all toys under this manufacturer".
In the product.tpl add this code wherever you want the image to appear. If you cut and paste this code as is and insert it just after the "</TR></TABLE></TD>" code at around row 142, the image will appear to the right hand side in a column of it's own.
In product.php at the following code just after:
$main = "product";
$smarty->assign("main",$main);
(you should find it near row 50)
Code:
$thisManufactorer = $product_info["manufacturerid"];
$manufacturer = func_query("SELECT * FROM $sql_tbl[manufacturers] WHERE manufacturerid = $thisManufactorer");
$smarty->assign("manufacturer", $manufacturer[0]["manufacturer"]);
This is a great mod so I hope it works for you as well as it works for me.