Changing an objects background image on hover.

Hey guys, I'm back after quite the absence. I'm creating an RPG style game, similar to a mix of the classic RPG game series Might & Magic, mixed with Final Fantasy 10. Anyway, I haven't used C# in forever, and can't figure out how to make an object that I imported from Cinema4D change image textures onHover.

 using UnityEngine;
 using System.Collections;
 
 public class Load : MonoBehaviour {
     
     public Texture LoadBG;
     public Texture LoadBG_Hover;
     
     void Start()
     {
         setNormal();
     }
     
     public void setNormal()
     {
         renderer.material.mainTexture = LoadBG;
     }
     
     public void setHover()
     {
         renderer.material.mainTexture = LoadBG_Hover;
     }
     
     void OnMouseOver()
     {
         setHover();
     }
     
 }

What exactly am I doing wrong?