Head over to the Hotel City Bellboy's hotel (currently showcasing the new San Francisco theme), and you can catch a demonstration of the game's newest outdoor decoration -- Fireworks.
Of the three July 4th items in the game's meager release, theFireworks is the most impressive of the bunch. Costing 4 Playfish Cash, one set of Fireworks consists of 3 little star-spangled rocket tubes that continually shoot out a fireworks show. You can find it under "Ground Decorations" at "Build" (the hammer icon), though the rockets can also be set on rooftops.
The other two items are at the "Redecorate" menu (little red coach icon). In "Wall Items" is a 4th of July banner for 3 PFC. And under "Ceiling Items" is a set of 3 blue, white, and red Balloons costing 2 PFC.