Hello Aviram,
You should only need to set the SonarQube server base URL (Property sonar.core.serverBaseURL) to what is the externally visible URL of your SonarQube server for the icons to show.
This is accessible from SonarQube menu Administration → General → Server base URL.
SonarQube knows himself as http://localhost:9000 by default (if base URL is not set), and all links to SonarQube (including icons) would use this improper base URL.
you should change the base URL into <YourSQpublicURL>:80 (the :80 is probably not needed, this is implicit).
Re-run a analysis to refresh the URL of the icons.