How do I make my GUI a different texture?

I want to make my 'Lives : 5' custom with my own font/texture. Here is my script. What do I need to add? Noob! Btw this is with C#.

 using UnityEngine;

using System.Collections;

public class PlayerStatusController : MonoBehaviour {

 public int Lives = 5;
         
 public ParticleEmitter EnemyExplosionEffect;
     
 public void OnGUI() {
     GUI.Label(new Rect(20, 20, 100, 20), System.String.Format("LIVES: {0}" , Lives));
 
 }
 public void OnTriggerEnter(Collider collider) {
     Lives--;
         
     Vector3 enemy_position = collider.transform.position;
     Destroy(collider.gameObject);
     
     ParticleEmitter explosion = (ParticleEmitter)Instantiate(EnemyExplosionEffect, enemy_position,Quaternion.identity);
     explosion.Emit();
     
     Vector3 explosionPos = transform.position;
     Collider[] colliders = Physics.OverlapSphere(explosionPos, 5.0f);
     
     foreach (Collider hit in colliders) {
         if (!hit) {
             continue;
         }
         
         if (hit.rigidbody) {
             hit.rigidbody.AddExplosionForce(500.0f, explosionPos, 5.0f);
             
         if (Lives == 0) {
             Application.LoadLevel ("GameOver");
         if (Lives == 0) {
             Screen.lockCursor = false;
         
                 }
             }
         }
     }
 }

}