With the exception of the App Store icon—which must be named iTunesArtwork—you can name your icons anything you want. Use image asset entries in your Xcode project for your app’s icon files. To add icons, assign the corresponding image files to the image assets of your project. At build time, Xcode adds the appropriate keys to your app’s Info.plist file and places the images in your app bundle. iOS chooses an icon based on whether its size is appropriate for the intended usage. To learn more about asset catalogs, see Asset Catalog Help.
For all images and icons, the PNG format is recommended. You should avoid using interlaced PNGs.
The standard bit depth for icons and images is 24 bits.