A new feature called profile banner is available in XenForo. The one problem I see with it is the image is also included in the member card which makes links in the member card difficult to see.
To disable the Upload a profile banner, do this:
Admin control panel -> User groups & permissions -> Registered -> Upload a profile banner -> No
To disable the Upload a profile banner, do this:
Admin control panel -> User groups & permissions -> Registered -> Upload a profile banner -> No
