“Train kept a rollin’ all night long…” “Down around the corner half a mile from here, see them long trains run and you watch them disappear…” Trains. They are in songs, movies, and a metaphor for steady movement. And they are ripe for GIFing- given their regular repeated motion.
Capture the essence of train movement in a GIF, and do what you can to keep it under 1 Mb (much of the train passing is repeated and you can delete frames and not lose the motion). Step it up a notch and match your train gif to a song using http://gifsound.com.