How do I resize the image on a GUILayout?

I need help to resize the image on my GUILayout so the images are placed add middle of the screen please help me :)

 var ResumeGui : GUIStyle;
 var RestartGui : GUIStyle;
 var MainMenuGui : GUIStyle;
 
 var Player : Transform;
 private var GuiEnabled = false;
  
 function Start(){
  Time.timeScale=1;
  GuiEnabled = false;
  
  
 }  
 
 function Update(){
  if(Input.GetKeyUp("escape")){
   if(GuiEnabled==true){ 
      GuiEnabled = false;
      Time.timeScale=1;
      AudioListener.volume=1;
      Screen.showCursor=false;
     }
     else if(GuiEnabled == false){
      GuiEnabled = true; 
      Time.timeScale=0;
      AudioListener.volume=0;
      Screen.showCursor=true;
 }
 }
 }
 
 
 function OnGUI(){
   if(GuiEnabled==true){ 
    if(GUILayout.Button (".", ResumeGui)){
      Time.timeScale=1;
      AudioListener.volume=1;
      Screen.showCursor=false;
      GuiEnabled = false;
      }
     }
   if(GuiEnabled==true){ 
    if (GUILayout.Button (".", MainMenuGui)){  
      Time.timeScale=1;
      AudioListener.volume=1;
      GuiEnabled=false;
      Application.LoadLevel(0);
     }
    }
   if(GuiEnabled==true){ 
    if (GUILayout.Button (".", RestartGui)){  
      Time.timeScale=1;
      AudioListener.volume=1;
      GuiEnabled=false;
      Player.position.x = 320.8074;
      Player.position.y = 20.97857;
      Player.position.z = 70.35075;
      Player.rotation.x = 0;
      Player.rotation.y = 0;
      Player.rotation.z = 0;
      Player.rigidbody.velocity = Vector3.zero;
      Player.rigidbody.angularVelocity = Vector3.zero;
    }
   }
   
 }