Thanks for posting! Our filter on Mac is device-wide. This means we should enforce SafeSearch across all browsers, regardless if you're in a Private Window. If SafeSearch is not working in a Private Window, check what version of Covenant Eyes you are running. If you are not running the latest version, uninstall Covenant Eyes12 and re-install7.
You can also use an alternative search engine that doesn't have any image results. A popular search engine with no image results is gopher.com17. If you want to use Gopher instead of Google, add google.com13 to your Custom Website List7 and then set gopher.com18 as your default search engine.
I hope this helps,