In Blackboard Ultra, banners can give your course a unique touch and help students differentiate between courses by displaying an image of your choice across the top of your Ultra course. This image will also appear as a thumbnail image on the Courses page before students enter your course.
You can add or change the banner image by clicking Course Image from the left menu within your Blackboard Ultra course, as seen in the image below.
You can also change the banner by selecting the 3 dot menu on your course within the Courses link (see image below).
For instructions and guidance on the best practices for banner images, view this Blackboard article.