The icon in script console (http://localhost:8080/script) can not be displayed, due to the lack of a getIcon() method in jenkins.model.Jenkins or hudson.model.Hudson.
The script console on a jenkins agent has a icon, but the wrong one: http://localhost:8080/computer/<agent_name>/script
Code changed in jenkins
User: Raphael Pionke
[FIXED JENKINS-37814] make the icon of the script console configurable (#2528)
The fix has been released in 2.21