Darkness below. Punctuated by the lights of civilization: home lights, street lamps, flood lighta, car headlights moving along the roads, perhaps shimmers of moonlight or late-dusk light on rivers and lakes...and, further punctuating the dark, fireworks.
I've never watched fireworks from above.
Would the patterns look much different from above? Likely not. They would be farther away: the plane may be leaving from or arriving at its airport and be somewhat low, or the plane may be at cruising altitude. How visible would fireworks be from cruising altitude? You may see them from farther away, but perhaps you'd see more of them: displays across a metro area, or isolated celebrations in small towns or perhaps even individual residences -- maybe farms, or tribal reservations where more powerful fireworks may be allowed by tribal laws. How large would the displays seem?
You may see flashes across a wide expanse of the dark land below you. For how long? How soon would you move past the displays? How much would they be blocked by your airplane's wings and fuselage? Would you need to crane your neck to see some? What affect would they have when you cannot hear them, due to their distance and the noise of the plane? Would you have time to see an entire display before you flew away from that chunk of the world? What displays would you see next? And would they, perhaps, somehow, be overwhelmed by the expanse of dark? In some way, it might look -- different.
I hope someday that I fly on a future July 4th night. Another experience to experience from a different direction -- literally.