My coop is small, holds only the three chickens. The Leghorn was totally NAKED so we put a lamp out in the chicken yard, aiming the light toward the door that goes from the coop to the yard so there would be some heat for her to enjoy. At no time does it get hot near where she sits in the doorway and It doesn't shine into the coop so they have the combined body heat to keep them warm, and nothing is near the lamp that could catch fire. It's attached to a metal fence rail, not flammable, and they can't get near it. They like to sit in the light when they come down to eat, and since it gets pretty cold her in the Pacific Northwest, having a lamp in the chicken yard doesn't shine in the sleeping area, so think I'm safe....and so are they.
I do like your coop, it's lovely! Mine is very small, just room for the three girls on the roost and their egg box is inside, attached through the outside wall. Everyone has to do what they feel comfortable with, and knowing they have a warm light to sit under makes ME happy. Oh, yes, the light is on a timer, on during the night, off during the day, so my electricity bill is not a problem. Wouldn't be if it was on 24/7. A local commercial chicken farm has lights on inside the big building for their 300+ chickens and it seems to do just fine.