It's a good start and good that you're prepared to modify/expand. When you have time, check out all of the great coop information - small, medium, large coop articles on BYC for inspiration!
Super cute. I hate to be a downer here but when you say that your coop arrived in a cardboard box....... Are those standard size chickens? In a pre-fab type coop? If so, get ready to modify it not long after you move them to it (they're typically way to small.) Or hopefully I'm wrong and you...