Chris,
Cass is great fun. There is the old company town, with the company store, school and houses, the ruins of the old sawmill and the railroad shops located about 1/4 mile away. I've always found them very willing to let people take photos up at the water tank and around the shops. If you ask, they will probably give you a brief shop tour.
There are three trips, the short trip up to Whittaker and the logging camp exhibit. This runs two times per day and you can go up on one train and back on another, which will let you take photos of the train coming up the steep 8% grade into Whittaker. The long trips are the Bald Knob trips on Sat & Sun and Tues - Thu, with the Spruce trip on Friday only. These are five hour trips and leave at 10:30. If you take the Bald Knob train, take warm clothes and jackets, even if it's warm when you are in Cass, as you gain a lot of elevation and it can be cold and windy up at the top, or even foggy.
Have a good trip.
Michael