Need for Speed Heat has many collectibles in the form of billboards, flamingos and street graffiti. They open as the level increases, and for the collection of all these items you will get new cars and bonuses.
So, in Heat you can find:
85 billboards (Nissan GT-R Nismo, smoke and decal set for cars)
100 flamingos (Porsche Cayman GT4, smoke and decal set for cars)
130 street graffiti (Nissan 370Z Nismo and a set of decals for cars)
A map with the exact location of all objects