The ornamental design for a wallplate, as shown and described.
FIG. 1 is a perspective view of a wall plate showing our new design;
FIG. 2 is a front view thereof;
FIG. 3 is a right side view thereof, the left side view being the mirror image thereof; and,
FIG. 4 is a top view thereof, the bottom view being the mirror image thereof.
The broken lines shown in the drawings depict portions of the article that form no part of the claimed design. The broken away symbols in the drawings illustrated along the center of the article indicate that any portion of the article beyond what is shown forms no part of the claimed design. The rear of the article is not part of the claimed design, and so the rear view has been omitted.