The ornamental design for a pillowcaseset, as shown and described.
FIG. 1 is a right side top plan view of an outer pillowcase layer of the pillow case set shown in broken lines for illustrative purposes and does not form any part of the claimed design;
FIG. 2 is a left side bottom plan view of the outer pillowcase layer of the pillow case set of FIG. 1 shown in broken lines for illustrative purposes and does not form any part of the claimed design;
FIG. 3 shows a right side top plan view of my design for an inner pillow case layer of the pillow case set;
FIG. 4 shows a left side top plan view of my design for an inner pillow case layer of the pillow case set;
FIG. 5 shows a left side bottom plan view of my design for an inner pillow case layer of the pillow case set (with the right side bottom plan view being mirror image of);
FIG. 6 shows a front elevation view of my design for an inner pillow case layer of the pillow case set;
FIG. 7 shows a rear elevation view of my design for an inner pillow case layer of the pillow case set;
FIG. 8 shows a left side elevation view of my design for an inner pillow case layer of the pillow case set;
FIG. 9 shows a bottom perspective view of my design for an inner pillow case layer of the pillow case set;
FIG. 10 shows a top perspective view of my design for an inner pillow case layer of the pillow case set;
FIG. 11 shows a front right side top exploded plan view of my design for a pillow case set (with the front left side bottom exploded view being a mirror image of); and,
FIG. 12 shows a front left side bottom exploded plan view of my design for a pillow case set (with the front right side bottom exploded plan view being mirror image of).