The ornamental design for a tailgateinnerpanel, as shown and described.
FIG. 1 is a front perspective view of a tailgate inner panel showing our new design;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a top view thereof;
FIG. 5 is a bottom view thereof;
FIG. 6 is a side view thereof; and,
FIG. 7 is an opposite side view thereof.
It will be understood that the broken lines shown in the drawings illustrate portions of the tailgate inner panel that form no part of the claimed design.