Ask clients. I have said this for the past few years and even tried to help two people start it as a business because I have the clients that would buy the service.
Infographics are the visual persuader of our time. Yet they are in a truly unshareable format. When you see them in Facebook posts you can zoom in to most and you have to go through effort to soak it all in.
Everytime a user has to fiddle with one to make it fully viewable it lessens the “end plus” effect of the experience.
On the other part of the internet you have twitter headers, youtube headers AND facebook headers.