I don't know if that tut covers linear lighting, shoot Nilla or David a pm.

You may want to, at the very least, repeat the texture a few times.

Linear lighting is a shading/lighting setup where the shading and illumination input don't have gamma pre-baked into it and thus the image does not look horrendous when tonemapped for example. And tonemapping goes a long way into making renders more believable since now you can use light falloff that is much closer to the real world without them looking like super novas.