Take a look at Image Handler 2 in the Free Software Add Ons section (link above). I use IH2 but none of the sites I manage use multiple images for products, but it looks like it has a utility to add additional images.

Edit:

Link to IH2 http://www.zen-cart.com/index.php?ma...roducts_id=117

From the description:
* Manage your multiple images for products easily from one page just like you do with attributes in the Products Attribute Manager.