The ornamental design for a headboard, as shown and described.
FIG. 1 is a front elevational view of a headboard showing my new design;
FIG. 2 is a top plan view; and
FIG. 3 is a left side elevational view.
From the rear the edges of the headboard sides and bottom are plain, and
the center panel, which includes caning, is substantially identical to the
front.