Problem Image GUI

Greetings,

I am making a GUI but when I try to create a Label which is a texture, then it doesn't draw the texture. The reason is that in theory mi image is NULL, so there's no image linked to the var.

However, I have attached the image using the inspector, and I don't undestand why this happen. Here is the code:

 var Skin : GUISkin;
 
 var img : Texture2D;
 
 var speed : int;
 var fuel : int;
 var oxygen : int;
 var gravity : int;
 var coins : int;
 
 function FillLabels(s : String, f : String)
 {
     flabel=f;
     slabel=s;
 }
 
 function OnGUI()
 {
     GUI.skin=Skin;
     
         GUI.Label ( Rect ( Screen.width/2, Screen.height/2, 65, 65 ), img );
 }