All kinds of things were taxed, including playing cards, bank checks, and matches. Photographs were added relatively late (1864-1866), so they didn't have their own tax stamp. That's why you will often see a Carte de Visite with a playing-card revenue tax stamp or a more generic proprietary tax stamp on the back. A 2-cent tax stamp indicates that the photograph cost up to 25 cents. More expensive photographs might have a 3-cent stamp.
Photographer: R.R. Rundell, Owego, New York.
Photographer: F. Smith Hooker, Havana, New York.
Photographer: D.W. Grout, Pulaski, New York.
Photographer: Crum & Sharp, Watkins, New York.
Photographer W.C. Crum, Penn Yan, New York
Photographer: George W. Barnes, Rockford, Illinois (Compliments of H. White)
Photographer: Masterson & Wood, 74 and 75 Arcade, Rochester, New York