Although the sky is dramatic enough to stand on it’s own as an imposing image, I’d say that given the direction of the light you can create a convincing composite by adding a foreground subject in black silhouette. The light and color create the perfect situation to experiment! You can superimpose some electric poles and telephone lines disappearing diagonally into the distance, a piece of someone walking past the camera (like a leg or an arm), a helicopter in the sky, etc. As long as you have a defined line and a perfectly black shape, it might work really well!

Having said all that, this is a magnificent image. What kind of filter(s) did you use?