Install this add-on and it will be automatically ready to use it.
Now if you take a look at any product form you will see a new menu Images
. Then click it and there you must see something like this:
Now if you want to add a new image it's fairly simple even though you are in a product variant or in a product template.
You can also create common categories of images for different products!With this library you will be able to have a gallery of images of any product (Variant and Template). This way you don't need to use some external cloud services provider.