The choice is up to you; by default, the App Store should give you plenty of options in terms of custom icons you can use. The third category of launchers supported by this shortcut are ...

1. On the iPhone's lock screen, touch and hold anywhere on the display until you see the Customize button. You'll need to ...

With iOS 18, Apple is finally opening up ... and it will even let third-party developers define specific dark mode app icons.