The ornamental design for a decorative lightsconce, as shown and described.
FIG. 1 is a perspective view of a decorative light sconce showing my new design.
FIG. 2 is a front view of a decorative light sconce showing my new design.
FIG. 3 is a rear view of a decorative light sconce showing my new design.
FIG. 4 is a left-side view of a decorative light sconce showing my new design.
FIG. 5 is a right-side view of a decorative light sconce showing my new design.
FIG. 6 is a top view of a decorative light sconce showing my new design; and,
FIG. 7 is a bottom view of a decorative light sconce showing my new design.
The design is directed to the ornamentation applied to the decorative light sconce. The switch and electrical box and internal housing for the light bulb are shown in broken lines. The broken lines form no part of the claimed design.