This is an example page that shows all of the customer-uploaded images for this shop.  It's simple to set this up if all of your products have only one image uploaded by you.  If that's the case, follow these steps:

1. In your shop's administrative area, go to Themes -> Template Editor
2. In the Template Editor, on the left side of the page, click "add a new template"
3. Choose the "page" type from the drop down menu that comes up, and call it "gallery"
4. Click "Create template"
5. Select your newly-created template (it will be called page.gallery.liquid) on the left side of the page
6. Copy the text below and paste it into the template:
   

   {% for product in collections.frontpage.products %}
   {% for m in product.images %}
        {% if forloop.first %}
            {% comment %}Ignore the first image{% endcomment %} 
        {% else %}
            {{ m | product_img_url: 'medium' | img_tag }}
        {% endif %}
   {% endfor %}
{% endfor %}

7. Save your new template.
8. In the "Blogs & Pages" section of your shop's administrative area, click "Create a new page."  I called mine "Gallery" (it's this page!) but you can call it anything you want.  "Our widgets in action" or "See who's loving their superscarves" would be fine too.  You can add text to the body of the page also.  
9. Then click the "Create Page" button.
10. Set the Page Visibility to "published" and the Page Template to "page.gallery"
11. Visit the page in your shop - the images uploaded by your customers should be visible!
    Note: you might need to add a link to the newly-created page to your shop's navigation