The idea of making a train was appealing to me, but I first decided to make the rubiks cube sitting on my desk.
Then I moved on to the train, deciding to make a night scene:
I used this train as a reference:
I started building out the shapes using primitives. As discussed in the series up to this point, multiple features of the train (the wheels for instance) were worked out and then duplicated. The night scene consists of a spotlight at the front, an area light, a point light, and two suns (one working in place of the moon, and one with shadows unchecked working as a purple fill light). The area light was implemented to get a bit more of an intense rim light near the front of the train, and the point light sits inside of the cab.
All of this together took me roughly 7 hours of work to do.