The ornamental design for pair of skull earpieces, as shown and described.
FIG. 1 is a perspective view of a pair of skull earpieces incorporating my design with the associated parts illustrated in phantom;
FIG. 2 is a side view of the pair of skull earpieces with the associated parts shown in phantom, with the opposite side view being identical;
FIG. 3 is an end view of the pair of skull earpieces illustrated in FIG. 1 with the associated parts being shown in phantom, with the opposite end view being identical;
FIG. 4 is a top view of the pair of scull earpieces with the associated parts being shown in phantom; and,
FIG. 5 is a bottom view of the pair of skull earpieces with the associated parts being shown in phantom.
The broken lines are included for the purpose of illustration and form no part of the claimed design.