From Apple's Human Interface Guidelines, you should provide all kinds of sizes for your alternate icon.
In your case, you should provide the icon of watchOS app's size.
Like your primary app icon, each alternate app icon is delivered as a collection of related images that vary in size. When the user chooses an alternate icon, the appropriate sizes of that icon replace your primary app icon on the Home screen, in Spotlight, and elsewhere in the system. To ensure that alternate icons appear consistently throughout the system—the user shouldn't see one version of your icon on the Home screen and a completely different version in Settings, for example—provide them in the same sizes you provide for your primary app icon (with the exception of the large App Store icon). See App Icon Sizes.
How to:
the value of CFBundleIconFiles
in info.plist
is an array. You should fill it with the names of icon files:
- no @2x @3x suffix
- no force rules about file naming, app will automatically pick the right solution for the sense it needs.
- no care about order