You can have several top site banners running in a loop on your registration site. Just make sure that all banners have the same height.
Choose Top site banner from the list – the type Banner can also be inserted, but this is more of a page breaker.
When you have uploaded your banner images, you need to check your settings.
If the banner image is not showing on your registration site, then check if the Reg. site banner is activated in Sections.