In organisation profile- page, you can set the default head banner, and logo for job ads/video interviews. You can also set default career site language, and URL, if you have job positions enabled.
You can add a background image by clicking 'Add background image'. Recommended banner image size is 1440px*320px or higher.
You can add an organisation logo by clicking 'Select logo'
You can find Organisation profile by opening 'Account Management' and selecting 'Organisation Settings' -> 'Organisation profile'.