The template responsible for rendering the product display is node--product--type.tpl.php found in the following directory: /commerce_kickstart/modules/commerce_kickstart/commerce_kickstart_product_ui/theme
This template generates 2 columns, the first contains the product image, and the second contains the product title, description, cart, etc.
Lines 13, 14 and 15 of the module generate the div which defines the column with the photo.
13 <div class="container-24 grid-14 prefix-1 clearfix"> 14 <?php print render($content['product:field_images']); ?> 15 </div>
If in defining a new product type you attach the image field to the variation, this code works. If however you attach the image field to the content type, the reference is incorrect. Instead of $content['product:field_images'], it should be $content['field_images'].
The project documentation states that you should be able to add images to the content type, so the theme layer should handle this possibility:
Per Product Display
You can follow the same procedure above to add an image gallery to your product displays. The advantage or difference is that you are adding the image field to the Content Type or the "group" of products. So, if you were selling tshirts and just had one image, this is how you would set that up.
A related problem is that if you use any image field except the existing field_images field, the same problem will occur, since the field id is hard coded into the template.
A workaround for anyone who needs a solution now is to copy node--product--type.tpl.php to the /profiles/commerce_kickstart/themes/commerce_kickstart_theme/templates directory, and rename it to node--YOURPRODUCTNAME.tpl.php. This will override the template for a specific product, and you can then edit the file as necessary to accomodate the image variable you are using.
YOURPRODUCTNAME must be the machine name of your product's content type, replacing any underscores (_) with dashes(-). To find the machine name of your content type, go to Content--> Content Types, and next to the name of each content type you'll see the machine name.
For example, if you see "Product display (Machine name: product_display)", then the machine for is "product_display". If you want to override the Product display node theming, then you have to copy the above mentioned template to node--product-display.tpl.php.