The ornamental design for a pillowsham, as shown and described.
FIG. 1 is a front view of a pillow sham showing my new design;
FIG. 2 is a bottom perspective view showing the pillow sham;
FIG. 3 is a top view showing the pillow sham;
FIG. 4 is a bottom view showing the pillow sham;
FIG. 5 is a left side view showing the pillow sham; and,
FIG. 6 is a front perspective view showing the pillow sham as used.
Right side views not shown are mirror images of left side views. Rear views not shown are mirror images of front views. The broken lines shown in the drawings are for the purpose of illustrating environment that forms no part of the claimed design.