The ornamental design for a wallpanel, as shown and described.
FIG. 1 is a perspective view of a wall panel illustrating of my new design;
FIG. 2 is a right side elevation view thereof;
FIG. 3 is a front elevation view thereof;
FIG. 4 is a rear elevation view thereof;
FIG. 5 is a top plan view thereof;
FIG. 6 is a bottom plan view thereof; and,
FIG. 7 is a perspective view of two wall panels interengaged with one another.
The broken lines are for illustrative purposes only and form no part of the claimed design. The claimed design is broken on one side to indicate indefinite length.