Here is a small airport that has one of the best indoor observation areas that I have seen. It is a two story atrium in the center of the terminal, outside the security area so that non-passengers can come in. There are chairs on both floors facing the airside ramp with floor-to-ceiling windows. On the second floor there are old photographs on the walls depicting memorable moments in aviation in the history of this region and old photos of the airport. There is also a flight schedule monitor and control tower audio on the speakers.
The view faces the center of the main runway and the ramp so you can see all of the traffic. As for photography, you are facing north so it has pretty good light almost all year, except maybe summer evenings. Since this is a small airport there isn’t a lot of traffic – almost all traffic is Regional Jets from Delta Connection and United Express but the view is superb. If you are traveling through the area I would recommend a visit here. In the photo examples below there is a picture of this observation area.