The ornamental design for decorative piece for footwear, as shown and described.
FIG. 1 is a front perspective view of a decorative piece for footwear showing my new design;
FIG. 2 is a left side view of the decorative piece shown in FIG. 1;
FIG. 3 is a right side view of the decorative piece shown in FIG. 1;
FIG. 4 is a front view of the decorative piece shown in FIG. 1; and,
FIG. 5 is a top view of the decorative piece shown in FIG. 1.
The broken line showing of the sole, heel, heel cap, portion of the upper and portion of the front is for illustrative purposes only and forms no part of the claimed design.