Facebook Canvas Web Banner allows you to load an external web page as a banner that will be displayed above your Unity app when hosted on Facebook.
You can use this banner space to promote your other games, platforms, display high score lists, or whatever you want. Adjust the banner height to fit your needs.
You will need to host the web page and Unity app from a secure website with a SSL certificate. The manual also has instructions on free hosting for Facebook.
Facebook Demo App (must be signed into Facebook to see it)
Web Banner and Unity Apps will need to be fixed at 760px on the Facebook canvas. For apps that are narrower, black bars will be displayed along the sides. The heights are fully adjustable.