There are examples of well and poorly designed billboards all over highways and high-traffic roads in the United States and other countries. However, Branislav Kropilak has a slightly different perspective on billboards that turns every-single-one into a work of art.
Also worth checking out are his photo exhibitions of Garages, Landings, Trains, Factories, and Lobbies.
Source: Branislav Kropilak: Billboards.