Banners can give your course a unique touch and help students differentiate between courses by displaying an image across the top of your course. This image will also appear as a thumbnail image on the Courses page before students enter the course.
To change your course banner, under course Details & Actions, select "Edit display settings" in the Course Image section.
You can also change the banner by selecting the 3 dot menu on your course within the Courses tab (see image below).
For instructions and guidance on the best practices for banner images, view this Blackboard article.