The ornamental design for a cosmeticshell, as shown and described.
FIG. 1 is a perspective view of a cosmetic shell showing my design;
FIG. 2 is a top view thereof;
FIG. 3 is a bottom view thereof;
FIG. 4 is a right side view thereof;
FIG. 5 is a left side view thereof;
FIG. 6 is a front view thereof; and,
FIG. 7 is a rear view thereof.
The dash-dot-dash broken lines illustrate the bounds of the claim. The remaining broken lines illustrate portions of the cosmetic shell. None of the broken line disclosure forms part of the claimed design.