The ornamental design for a petcostume, as shown and described.
FIG. 1 is a front, perspective view of a pet costume showing our new design;
FIG. 2 is a front view thereof;
FIG. 3 is a front view thereof with a dog portion of the environmental subject matter removed for clarity;
FIG. 4 is a rear view thereof;
FIG. 5 is a right side view thereof;
FIG. 6 is a left side view thereof; and
FIG. 7 is a top view thereof.
FIG. 8 is a front, perspective view of the pet costume of FIG. 1 with additional environmental subject matter illustrated in broken lines;
FIG. 9 is a front view thereof;
FIG. 10 is a front view thereof with a dog portion of the environmental subject matter removed for clarity;
FIG. 11 is a rear view thereof;
FIG. 12 is a right side view thereof;
FIG. 13 is a left side view thereof; and,
FIG. 14 is a top view thereof.
The features shown in broken lines are portions of the pet costume or environmental subject matter to the pet costume forming no part of the claimed design. The features shown in long dash-short dash bolded broken lines indicate the bounds of the claimed design and otherwise form no part of the claimed design. Bottom surfaces of the pet costume are not claimed, and therefore, the bottom views are omitted from this application.