Add texture to my start menu button

This is my code for my Exit game button I was wondering if there is any way to make a texture for it.

function OnGUI () {

if (GUI.Button (Rect (400,500,200,40), "Exit Game")) {

     Application.Quit();
     
     

     
}}

You can use either a GUIStyle or a GUIContent. The second one won’t be streched.