GUI depth?

I have script :

function OnGUI () {
GUI.BeginGroup (Rect (0, 0, Screen.width,Screen.height));
GUI.DrawTexture(Rect(0,0,Screen.width,Screen.height),mp_mars);
GUI.EndGroup ();
}

it’s make a GUI.Texture and i have a gameobject what i want to place front of the Texture.
Is it possible?

You can probably follow this: