I dont know if is right way... but... have many pages with same problem: old frontend images.
This pages have ALL images old (checked yesterday):

All this manual pages need new images... the current images are from Zabbix 2 and the interface is very different.

https://www.zabbix.com/documentation/3.0/manual/web_interface/frontend_sections/monitoring/overview
https://www.zabbix.com/documentation/3.0/manual/web_interface/frontend_sections/monitoring/web
https://www.zabbix.com/documentation/3.0/manual/web_interface/frontend_sections/monitoring/latest_data
https://www.zabbix.com/documentation/3.0/manual/web_interface/frontend_sections/monitoring/triggers
https://www.zabbix.com/documentation/3.0/manual/web_interface/frontend_sections/monitoring/discovery
https://www.zabbix.com/documentation/3.0/manual/web_interface/frontend_sections/monitoring/it_services
https://www.zabbix.com/documentation/3.0/manual/web_interface/frontend_sections/inventory/overview
https://www.zabbix.com/documentation/3.0/manual/web_interface/frontend_sections/inventory/hosts
https://www.zabbix.com/documentation/3.0/manual/web_interface/frontend_sections/reports/triggers_top
https://www.zabbix.com/documentation/3.0/manual/web_interface/frontend_sections/administration/queue