Backpack accessory

[0001]FIG. 1 is a front perspective view of a backpack accessory showing our new design;

[0002]FIG. 2 is a front view thereof;

[0003]FIG. 3 is a rear view thereof;

[0004]FIG. 4 is a right side view thereof;

[0005]FIG. 5 is a left side view thereof;

[0006]FIG. 6 is a top view thereof;

[0007]FIG. 7 is a bottom view thereof;

[0008]FIG. 8 is a front perspective view of a backpack accessory showing our new design in a state of use;

[0009]FIG. 9 is a front view thereof;

[0010]FIG. 10 is a rear view thereof;

[0011]FIG. 11 is a right side view thereof;

[0012]FIG. 12 is a left side view thereof;

[0013]FIG. 13 is a top view thereof; and,

[0014]FIG. 14 is a bottom view thereof.

[0015]The broken lines form no part of the claimed design. The dashed stitching lines form no part of the claimed design. The disclaimed environment depicted in FIGS. 8-14 is shown without some features for clarity of the backpack accessory.