The ornamental design for a napkinholder, as shown and described.
FIG. 1 is a front perspective view of a napkin holder showing a first embodiment of my new design, the front perspective view illustrating a front, a top, and a right side thereof, a left side view being identical to the right side view;
FIG. 2 is a top view of the first embodiment of my new design;
FIG. 3 is a bottom view of the first embodiment of my new design;
FIG. 4 is a front elevation view of the first embodiment, a rear elevation view being identical to the front elevation view;
FIG. 5 is a front perspective view of a napkin holder showing a second embodiment of my new design, the front perspective view illustrating a front, a top, and a right side thereof, a left side view being identical to the right side view;
FIG. 6 is a top view of the second embodiment of my new design;
FIG. 7 is a bottom view of the second embodiment of my new design; and,
FIG. 8 is a front elevation view of the second embodiment, a rear elevation view being identical to the front elevation view.
Napkins and straws are shown in broken lines for illustrative purposes only and form no part of the claimed design.