GUI.Box not showing Texture on device

I'm using GUI.Box in order to show the items status of my main character. It works well when I test it in Unity's simulator but the Texture doesn't even show in a real device. I've tried using both Texture and GUITexture but none of them works.

I'm using Resources.Load and this can be part of the problem. Here's the function I call the textures from:

 Texture loadTextureFromString(string name)
 {
     string path = "Assets/GUI/items/" + name + ".PNG";
     return Resources.LoadAssetAtPath(path, typeof(Texture)) as Texture;
 }

Or the equivalent changing the texture files type to GUI and writing GUITexture instead of Texture.

And, my OnGUI() function looks like this:

 void OnGUI()
 {
     Texture itemDisplayed = loadTextureFromString(someStringVariableThatChanges);
     GUI.Box(new Rect(kX, kY, kWidth, kHeight), itemDisplayed, GUIStyle.none);
 }

Any idea of how to solve this issue? Thanks a lot.