1.
advertising tower; billboard pillar
A tall structure or tower used to display advertisements, typically found in urban areas.
2.
figurehead; poster child; public face
A person who serves as the public representative of an organization or cause, often implying they are being used mainly for promotional purposes.
Usage
The figurative sense (sense 2) is very common in news reporting, especially when discussing celebrities or public figures who lend their name and image to organizations, sometimes unknowingly or for dubious purposes.