I just noticed that iTunes' notification icon was replaced by album covers:

And it's app icon was a small one near the title, which is a bit different from the ones I knew of:

Where I can only add images as part of the content, not the app icon.
Is there an undocumented NSUserNotification API that I didn't know?
NVM, I found the answer.
iTunes use private APIs.
NSUserNotification *notification = [NSUserNotification new];
[notification setValue:anImage forKey:@"_identityImage"];
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