Did you watch the video? He stated he left a link the description with all the assets. There's a link in the associated article too. Unfortunately, the links are broken though. Just search the web for the icon/image you want (i.e. "iChat icon"), then create a shortcut and change it to use that image/icon.
Keep in mind that iOS app icons are always square. So if you want it to be like his where the FaceTime icon is a bubble shape, then a lot more work is involved. The background of the app icon has to match up perfectly with the wallpaper behind it. That makes the background of the app icon "transparent" and gives the illusion that the app icon isn't a square. (The parallax effect has to be disabled too, so the wallpaper doesn't move.)
There are apps out there to help you create these icons with the background once you find some you want to use. This video shows you how it's done.