When viewing a page that contains sub-pages, they will be displayed as buttons by default
You can update the main page to display any sub-pages as images too. The first product added to any sub-page will be used as the cover photo, however you can also upload custom photo.
1
Select 'Pages'
2
Edit the parent page
3
Scroll down to 'Security & Visibility'
4
Set 'Display sub-pages automatically if available' to 'Images'