I have created a (very quick and dirty) module that will allow you to store 22 product images inside the product form that can be pulled into your custom website template using by adding some logic to your website's product view page.

Just clone the following git repository here into your /addons directory:

https://github.com/lukebranch/website_multi-image

and install as you would a normal Odoo addon. In order to add the product images into your custom website template's product page you can just use the following logic inside whatever div (or other tag) you'd like to duplicate for images:

t-if="not product.x_product_image_1 == null"

for example:

<div t-if="not product.x_product_image_1 == null">
<!-- Add your image container here -->
<span itemprop="image" t-field="product.x_product_image_1" t-field-options="{&quot;widget&quot;: &quot;image&quot;, &quot;class&quot;: &quot;product_detail_img&quot;}" class="img-responsive img-rounded"/>
</div>

Just change the _1 in the t-if statement and t-field statement above each time you want to add an extra image to the template, for example the following code adds image field 2:

<div t-if="not product.x_product_image_2 == null">
<!-- Add your image container here -->
<span itemprop="image" t-field="product.x_product_image_2" t-field-options="{&quot;widget&quot;: &quot;image&quot;, &quot;class&quot;: &quot;product_detail_img&quot;}" class="img-responsive img-rounded"/>
</div>

The t-if statement is designed to check if a product image field contains an image, and if not, just hide what is contained inside that tag.

While this is certainly a quick and dirty method and is not by any means the ideal way to accomplish this, it does allow you to have multiple images on your product page and will allow you to import and export images using the field names (eg: x_product_image_2) to allow for mass import/export and mass updates by CSV.

Please comment back if you run into any issues and create an issue on the github repository for this module if you find a bug:

https://github.com/lukebranch/website_multi-image/issues

I hope it helps!