I recently ran across this same problem.
Looked into the coding suggested for tpl_product_info_display.php, but it won't work, as I'm using a 3rd party javascript to get the facebook button on my pages.
So, I created an /images folder in my root directory. I copied over the entire contents of store/images, and now the facebook button functions with images. Only problem is how to keep the root's folder updated. For that I set up a background ftp-transfer standalone application on my desktop (I have to use one of these for a different aspect of the store anyhow).
Every day, when I add new products, I upload an image for each by way of the admin, and then I let them all sit overnight. In the middle of the night, they are ftp'd to the folder in the root directory automatically.
Not elegant, but it'll do.