GUI.Box can show an image (Texture) or a string but not both. You passing it a string. Unity does some behind the scene magic when your adding strings together so you don’t have to explicitly call ToString.
However, its what your doing… so your line here is actually this:
Now if you need to print the score on top of this image, you can try Gui.Text , though I’m not sure if there is an easy way to set the alpha to 0 for the non string portion of a gui.Text