iOSアイコンのAppicon.appiconset内にあるContents.jsonはアイコン作成サイトで作ったものを一部書き換えて使っています。
内容は以下の通りです。
{"images":[{"size":"60x60","expected-size":"180","filename":"180.png","folder":"AppIcon.appiconset/","idiom":"iphone","scale":"3x"},
{"size":"40x40","expected-size":"80","filename":"80.png","folder":"AppIcon.appiconset/","idiom":"iphone","scale":"2x"},
{"size":"40x40","expected-size":"120","filename":"120.png","folder":"AppIcon.appiconset/","idiom":"iphone","scale":"3x"},
{"size":"60x60","expected-size":"120","filename":"120.png","folder":"AppIcon.appiconset/","idiom":"iphone","scale":"2x"},
{"size":"57x57","expected-size":"57","filename":"57.png","folder":"AppIcon.appiconset/","idiom":"iphone","scale":"1x"},
{"size":"29x29","expected-size":"58","filename":"58.png","folder":"AppIcon.appiconset/","idiom":"iphone","scale":"2x"},
{"size":"29x29","expected-size":"29","filename":"29.png","folder":"AppIcon.appiconset/","idiom":"iphone","scale":"1x"},
{"size":"29x29","expected-size":"87","filename":"87.png","folder":"AppIcon.appiconset/","idiom":"iphone","scale":"3x"},
{"size":"57x57","expected-size":"114","filename":"114.png","folder":"AppIcon.appiconset/","idiom":"iphone","scale":"2x"},
{"size":"20x20","expected-size":"40","filename":"40.png","folder":"AppIcon.appiconset/","idiom":"iphone","scale":"2x"},
{"size":"20x20","expected-size":"60","filename":"60.png","folder":"AppIcon.appiconset/","idiom":"iphone","scale":"3x"},
{"size":"1024x1024","filename":"1024.png","expected-size":"1024","idiom":"ios-marketing","folder":"AppIcon.appiconset/","scale":"1x"},
{"size":"40x40","expected-size":"80","filename":"80.png","folder":"AppIcon.appiconset/","idiom":"ipad","scale":"2x"},
{"size":"72x72","expected-size":"72","filename":"72.png","folder":"AppIcon.appiconset/","idiom":"ipad","scale":"1x"},
{"size":"76x76","expected-size":"152","filename":"152.png","folder":"AppIcon.appiconset/","idiom":"ipad","scale":"2x"},
{"size":"50x50","expected-size":"100","filename":"100.png","folder":"AppIcon.appiconset/","idiom":"ipad","scale":"2x"},
{"size":"29x29","expected-size":"58","filename":"58.png","folder":"AppIcon.appiconset/","idiom":"ipad","scale":"2x"},
{"size":"76x76","expected-size":"76","filename":"76.png","folder":"AppIcon.appiconset/","idiom":"ipad","scale":"1x"},
{"size":"29x29","expected-size":"29","filename":"29.png","folder":"AppIcon.appiconset/","idiom":"ipad","scale":"1x"},
{"size":"50x50","expected-size":"50","filename":"50.png","folder":"AppIcon.appiconset/","idiom":"ipad","scale":"1x"},
{"size":"72x72","expected-size":"144","filename":"144.png","folder":"AppIcon.appiconset/","idiom":"ipad","scale":"2x"},
{"size":"40x40","expected-size":"40","filename":"40.png","folder":"AppIcon.appiconset/","idiom":"ipad","scale":"1x"},
{"size":"83.5x83.5","expected-size":"167","filename":"167.png","folder":"AppIcon.appiconset/","idiom":"ipad","scale":"2x"},
{"size":"20x20","expected-size":"20","filename":"20.png","folder":"AppIcon.appiconset/","idiom":"ipad","scale":"1x"},
{"size":"20x20","expected-size":"40","filename":"40.png","folder":"AppIcon.appiconset/","idiom":"ipad","scale":"2x"}]}