This post should display a large hero image at the top of a page.
This post tests a horizontal image using the following YAML Front Matter:
image:
path: /images/eder-oliveira-180877.jpg
Hero images can also be assigned more succinctly when thumbnail or caption are not used.
image: /images/eder-oliveira-180877.jpg
Tall images will push content down the page. 1600 x 600 is a good middle-ground size to aim for.