The ornamental design for a livestockpenwallpanel, as shown and described.
FIG. 1 is a front perspective view of a livestock pen wall panel showing our new design;
FIG. 2 is a front elevational view thereof;
FIG. 3 is a rear elevational view thereof;
FIG. 4 is a left side elevational view thereof;
FIG. 5 is a right side elevational view thereof;
FIG. 6 is a top elevational view thereof; and,
FIG. 7 is a bottom elevational view thereof.
The broken line representations of portions of the livestock pen wall panel in FIGS. 1-7 are shown for illustrative purposes only and form no part of the claimed design.