UI image component problems with Character Creation....

I am having trouble on finding out how to make my class slider work. It's a slider thats SUPPOSE to change the sprite image of the UI Image Component and is using static components for the character creation menu I'm making for it. The only problem is, it cant find the UI Image component and cant override the sprite. So Heres My Script and I just need to check if this would work.

using UnityEngine; using System.Collections; using UnityEngine.UI;

public class ClassSlider : MonoBehaviour {

 private float HSliderValue = 0.0F;
 private bool Slidervalue1;
 private bool Slidervalue2;
 private bool Slidervalue3;
 public Image CharacterDisplay;
 public Canvas Canvas;

 void ONGUI()
 {
     if (HSliderValue == 0.0F) 
     {
         Slidervalue1 = true;
         Slidervalue2 = false;
         Slidervalue3 = false;
     }

     if (HSliderValue == 1.0F) 
     {
         Slidervalue1 = false;
         Slidervalue2 = true;
         Slidervalue3 = false;
     }

     if (HSliderValue == 2.0F) 
     {
         Slidervalue1 = false;
         Slidervalue2 = false;
         Slidervalue3 = true;

     }


 }

 public void ModernNinja(float newValue)
 {

     if (Slidervalue1 == true)
     {
         CharacterDisplay.sprite = Resources.Load<Sprite> ("Players/Models/MilitaryNinja/Display")as Sprite;
     }
         
 }

}