This is an example of a product with no attached images. The image you see is “pulled” from a custom field. Hover for a larger version. The script used is called Magic Zoom and you can read more about it as well as purchase it here.
You are not restricted to this particular effect. You can choose between 4 different effects including jQzoom and Lightbox as well as no effects at all! Remember that you have full control over the image sizes from the theme settings.