概要

using System;
using UnityEditor;
using UnityEditor.Build;
using UnityEngine;

internal static class Example
{
    [MenuItem( "Tools/Example" )]
    private static void Run()
    {
        var icon             = AssetDatabase.LoadAssetAtPath<Texture2D>( "" );
        var namedBuildTarget = NamedBuildTarget.iOS;
        var iconKind         = IconKind.Any;

        var icons = PlayerSettings.GetIcons
        (
            buildTarget: namedBuildTarget,
            kind: iconKind
        );

        Array.Fill( icons, icon );

        PlayerSettings.SetIcons
        (
            buildTarget: namedBuildTarget,
            icons: icons,
            kind: iconKind
        );

        AssetDatabase.SaveAssets();
    }
}

参考サイト様