no, a wall sconce can't be installed. The 3" x 8" rule applies for certain fixtures. Read 410.4.(of the top of my head, maybe not right section but it should be close to that)
Wall sconces are not prohibited from 'the area'
410.4(D) Bathtub and Shower Areas. No parts of cord-connected luminaires (fixtures), hanging luminaires (fixtures), lighting track, pendants, or ceiling-suspended (paddle) fans shall be located within a zone measured 900 mm (3 ft) horizontally and 2.5 m (8 ft) vertically from the top of the bathtub rim or shower stall threshold. This zone is all encompassing and includes the zone directly over the tub or shower stall.
Bob
