If you use Unity Personal Edition to make your project, a default splash screen displays while your game loads. It is oriented according to the Default Screen Orientation option in the Player Settings. You cannot change this splash screen.
Unity Professional Edition users can change the splash screen. You can use any texture in the project as a splash screen. You can set the texture from the Splash Image section of the Android Player Settings. You should also select the Splash scaling method from the following options:-