I felt like the Safari icons for Big Sur/Monterey had too much 'chrome', so I made new ones.

For both plain ol' Safari and Safari Technology Preview (in 🌚 & 🌝)

For Safari Technology Preview:

Since Safari Preview is user-installed, the icon can be replaced without any third-party apps.

1. Open Get Info on Safari Technology Preview (right click the application in Finder)
2. Drag and drop the .icns file over the current icon at the top-left corner
3. That's it! Don't worry, you can always return to the default app icon by selecting the current icon in the Info window and pressing delete.

For Safari:

Here is my unsolicited plug for IconChamp. This is the only app I've found that can change the icons for system-installed apps like Safari in Monterey. It's not free, but I think it's awesome.

The only free work-around that I've come up with is to create a simple AppleScript to open Safari:

tell application "Safari" to activate

and export it as an Application, which can take the new icon using the same instructions above for Preview (Get Info > drag & drop the icns).