FIG. 1 is a perspective view of a floorboard cover of the present invention. FIG. 2 is a top side plan view thereof. FIG. 3 is a bottom side plan view thereof. FIG. 4 is a left side elevation view thereof. FIG. 5 is a right side elevation view thereof. FIG. 6 is a rear end elevation view thereof; and, FIG. 7 is a front end elevation view thereof. Those portions of the floorboard cover shown in broken lines form no part of the claimed design.