The ornamental design for lamphead, as shown and described.
FIG. 1 is a bottom perspective view of the lamphead, with a stirrup for the lamphead;
FIG. 2 is a front perspective view thereof;
FIG. 3 is top perspective view thereof;
FIG. 4 is another front perspective view thereof;
FIG. 5 is a back perspective view thereof;
FIG. 6 is a left side perspective view thereof; and,
FIG. 7 is a top perspective view thereof.
The power cord, the sheath at one end of the power cord, the attachments on the bracket arm, the bracket arm and washers, and the light bulb and sockets shown in broken lines and all other features shown in broken lines do not form part of the claimed design in this application.