It's not so easy to find fortinet images. Here are some working links (mostly for eve-ng labs) that e got from a nice course for nse4 certification:
[Hidden Content]
Download Router and Switches Images use 7Zip Application to Extract:
[Hidden Content]
Fortinet NSE4 Lab Images:
[Hidden Content]
CheckPoint Firewall Image:
[Hidden Content]
Window XP and F5 Image Link:
[Hidden Content]
Cisco SDWAN Images Link:
[Hidden Content]