Howdy,
in this situation, I would do the following:
Check if the given folder exists (/usr/share/zentyal/www/images/package-icons)
If not, set up a VM and copy the files from the VM to the original Server (and set User and group according to your system).
If it exists, check the permissions (cross-check with VM)
Maybe the Zentyal Firewall is blocking the traffic? Try to disable the FW Module and test again.
Are the server processes running? Please confirm with "netstat -tulpen" (as root / with sudo)
Kind Regards
Thomas