Feature summary: Templates that allow more content combinations, such as templates with two images or other non-standard arrangements. Also a vertical layout for mobile (image above, text below) available out of the box,

Use cases: Campaigns that need banners with multiple images or content layouts not covered by existing templates.

Benefits: Expands the range of banner designs achievable without custom code, making the editor useful for a wider variety of campaign needs.

More details here: https://phabricator.wikimedia.org/T424074#11901403