i have pondered building an indoor aviary for a little D'Anver we have that seems to be extra susceptible to mites. We bring her in every so often for treatment and keep her in a flight cage. i have seen very nice professional grade metal aviaries, mainly used for outside and super expensive. But i suspect you could construct a large pen from hardware cloth and 2 x 2's. Actually, you wouldn't really need hardware cloth if it's an indoor thing, just chicken wire. i actually love having birds inside, although they can get a little stinky.
Sorry i don't have anything concrete to offer in the way of pictures of finished indoor pens. But i know there are folks on here that keep birds inside. Hopefully someone will come along with pics. In the meantime, maybe do a search on indoor chickens. i would personally love to see some set-ups myself.