Add a full-width header image (like the image of a person holding a compass above) to any of your content blocks by uploading an image to the 'Thumbnail image for Facebook, etc.' field for your subpage, found under the Settings > Social media tab.
You can also add images to the body of your content block via the content editor. When doing so, make sure to set the width variable to a maximum of 518 and leave the hight value blank, like so:
Using Animated GIFs
If you're using animated gifs in your email blast, just be aware that they aren't supported for all email clients (like some older versions of Outlook). For email clients that don't support animated GIFs, typically the first frame of the GIF is displayed instead. Check out https://www.litmus.com/blog/a-guide-to-animated-gifs-in-email/ for more information.