I did this by putting
Code:
[img]mlogo.php?manufacturerid={$manufacturerid.manufacturerid}[/img]
wherever you need the manufacturer's logo to display in product.tpl. If you would like the logo to link to the page that views all of the manufacturer's products, use
Code:
<a href="manufacturers.php?manufacturerid={$manufacturerid.manufacturerid}">
[img]mlogo.php?manufacturerid={$manufacturerid.manufacturerid}[/img]</a>
Make sure you put the manufacturer's logo's in the admin side for this to display correctly. Otherwise, default_image.gif will show up.
An example of it in action:
http://www.heritagetoys.com/product.php?productid=16840&cat=0&page=1