For me, the best part of a Fourth of July celebration is the huge fireworks that spread out over the sky above me. It's stunning to see such beauty displayed from an explosion.
Trying to emulate it on cookies is harder than I thought it would be. Using wet-on-wet is always a time saver and makes for a quickly decorated cookie, but getting all the dots and flourishes in the right place to show a symetrical fireworks display is a bit tricky.
Start with a round or scalloped round cookie. Outline and flood it with a darker blue glaze.
While the glaze is still very wet, add circular patterns of differing fireworks. Use red, light blue and white glaze to form those patterns. My suggestion would be to find some clipart of fireworks and study those patterns before attempting the wet-on-wet piping.