I think for the train level I would want to feel more like I am moving fast. I think this would add a sort of foreboding rush and kinetic energy that you would get in a really well done car chase scene in a movie.
You could add more details to the scrolling background to communicate the movement, like a parallax effect with some jungles of buildings surrounding the train.
I also think adding layers of movement to the background like a train moving parallel to the level but slightly slower, or a sort of bridge going over the level with a train on it. things that appear and fly by in the background for a couple seconds during the gameplay.
Maybe you could add slight turbulence to everything as well as some swaying animations to the cords connecting the floating platforms.
Just some small details though, not that they have to make it in. I'm just a sucker for good train levels