Adding a Texture to a GUI Button?

I am using a main menu script that I found online to give me a starting point. It works great and I have exactly what I need, except one thing. For the level select screen, I am trying to add a picture to the GUI Button that takes you to a level. However, I am having trouble finding out how to do that. Here is my script in C#: `using UnityEngine;
using System.Collections;

using UnityEngine;
using System.Collections;

public class MainMenuScript : MonoBehaviour
{
public GUISkin GameSkin;

private bool _isFirstMenu = true;
private bool _isLevelSelectMenu = false;
private bool _isLoadGameMenu = false;
private bool _isOptionsMenu = false;

// Use this for initialization
void Start () 
{
	
}

// Update is called once per frame
void Update () 
{
	
}

void OnGUI()
{
	GUI.skin = GameSkin;
	
	GUI.Label(new Rect(30, 75, 300, 25), "Unnamed Racing Game Pre Alpha Build v0.0.1", "Menu Title");
	
	FirstMenu();
	LoadGameMenu();
	LevelSelectMenu();
	OptionsMenu();
	
	if(_isLevelSelectMenu == true || _isLoadGameMenu == true || _isOptionsMenu == true)
	{
		if(GUI.Button(new Rect(10, Screen.height - 35, 150, 25), "Back"))
		{
			_isLevelSelectMenu = false;
			_isLoadGameMenu = false;
			_isOptionsMenu = false;
			
			_isFirstMenu = true;
		}
	}
}

void FirstMenu()
{
	if(_isFirstMenu)
	{
		if(GUI.Button(new Rect(10, Screen.height / 2 - 100, 150, 25), "New Game"))
		{
			Application.LoadLevel("Level01");
		}
		
		if (GUI.Button(new Rect(10, Screen.height / 2 - 65, 150, 25), "Load Game"))
		{
			_isFirstMenu = false;
			_isLoadGameMenu = true;
		}
		
		if (GUI.Button(new Rect(10, Screen.height / 2 - 30, 150, 25), "Level Select"))
		{
			_isFirstMenu = false;
			_isLevelSelectMenu = true;
		}
		
		if (GUI.Button(new Rect(10, Screen.height / 2 + 5, 150, 25), "Options"))
		{
			_isFirstMenu = false;
			_isOptionsMenu = true;
		}
		
		if (GUI.Button(new Rect(10, Screen.height / 2 + 40, 150, 25), "Quit Game"))
		{
			Application.Quit();
		}
	}
}

void LoadGameMenu()
{
	if(_isLoadGameMenu)
	{
		GUI.Label(new Rect(10, Screen.height / 2 - 200, 200, 50), "Load Game", "Sub Menu Title");
		GUI.Box(new Rect(10, Screen.height / 2 - 100, Screen.width / 2 + 100, Screen.height - 450), "Choose Saved Game");
	}
}

void LevelSelectMenu()
{
	if(_isLevelSelectMenu)
	{
		GUI.Label(new Rect(10, Screen.height / 2 - 200, 200, 50), "Course Select", "Sub Menu Title");
		// Top Buttons
		if(GUI.Button(new Rect(10, Screen.height / 2 - 100, 200, 150), "Mountainous Bayside"))
		{
			Application.LoadLevel("Level1");
		}
		
		if(GUI.Button(new Rect(220, Screen.height / 2 - 100, 200, 150), "Level 02"))
		{
			
		}
		
		if(GUI.Button(new Rect(430, Screen.height / 2 - 100, 200, 150), "Level 03"))
		{
			
		}
		
		if(GUI.Button(new Rect(640, Screen.height / 2 - 100, 200, 150), "Level 04"))
		{
			
		}
		
		//Bottom Buttons
		if(GUI.Button(new Rect(10, Screen.height / 2 + 60, 200, 150), "Level 05"))
		{
			
		}
		
		if(GUI.Button(new Rect(220, Screen.height / 2 + 60, 200, 150), "Level 06"))
		{
			
		}
		
		if(GUI.Button(new Rect(430, Screen.height / 2 + 60, 200, 150), "Level 07"))
		{
			
		}
		
		if(GUI.Button(new Rect(640, Screen.height / 2 + 60, 200, 150), "Level 08"))
		{
			
		}
	}
}

void OptionsMenu()
{
	if(_isOptionsMenu)
	{
		GUI.Label(new Rect(10, Screen.height / 2 - 200, 200, 50), "Options", "Sub Menu Title");
		GUI.Box(new Rect(Screen.width / 2, 0, Screen.width / 2, Screen.height), "");
		
		if (GUI.Button(new Rect(10, Screen.height / 2 - 30, 150, 25), "Audio Options"))
		{
			
		}
		
		if (GUI.Button(new Rect(10, Screen.height / 2 + 5, 150, 25), "Graphics Options"))
		{
			
		}
	}
}

}`
If you look at lines 100-104, I am trying to add an image called “Image1” to that GUI Button and only that GUI Button. Can anyone help me do this?

If i understand right, you need to add a reference to the image

public Texture2D Image1;

if(GUI.Button(new Rect(430, Screen.height / 2 - 100, 200, 150), Image1))
{

}

as you can see in the unity scripting api here:
Unity GUI Button