In order to display additional images you need a main image to start with, it's usually the one uploaded when you add a new product, then you put all your additional images in the same file.
Usually the main image displays at the top of the product information screen, above the product details and all the additional images display below the product info, however with the removal of the Main Product Image code the main image doesn't show up anymore, What I did was name one of my images gallery.jpg, then made another copy of it and called it gallery_3.jpg so even though the gallery.jpg image doesn't display the gallery_3.jpg does.
You can leave the code in if you like but I like the look of it without better.
Does all that make sense?
Katie
www.live2knit.com.au