First, your URL is incorrect: you wouldn't include /usr/share/kibana/[etc], because that is the directory on your file system, not to an exposed URL directory in Kibana.
I would recommend looking at the other recommendation in that thread:
The better option, assuming you don't want to serve the image from some other service, would be to expose it via a Kibana plugin. That way you could easily upgrade Kibana and just re-install that plugin instead of modifying all the Kibana source again. The plugin would just need to use the same
server.exposeStaticDirmethod to expose a path inside the plugin. Bundle the image into your plugin, install it into Kibana, and now you can have the image hosted inside of Kibana. If you don't want to bundle the image, you could just have it serve assets from another path too, but that's a little more prone to breaking (if you change servers, for example).
I would refer to this discuss topic for details on properly exposing static images from a plugin, as well.
Hope this helps!