What makes a great fireworks show? This is a matter of personal preference, of course. But here are some general pointers.
Your show will look better with 3D models in the scene. For example, you can insert mountains, bridges, buildings, trees and much more. (read more about finding 3D models on the internet)
Note that FWsim currently does not allow to place fireworks on top of buildings. Fireworks are always at ground level. However, this feature will be added in a future version.