The ornamental design for a streetlamphead, as shown and described.
FIG. 1 is a perspective view of a streetlamp head showing our new design;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a left side view thereof, a right side view being a mirror image of the left side view;
FIG. 5 is a top plan view thereof; and,
FIG. 6 is a bottom plan view thereof.
The broken lines shown in the figures illustrate environmental structure and portion of the streetlamp head that form no part of the claimed invention.