The ornamental design for a seatbackholder for objects, as shown and described.
FIG. 1 is a front perspective view of a seatback holder for objects according to my new ornamental design. The seatback holder for objects is illustrated in use on an example seatback and holding an example object;
FIG. 2 is a front perspective view thereof;
FIG. 3 is a rear perspective view thereof;
FIG. 4 is a front view thereof;
FIG. 5 is a first side view thereof;
FIG. 6 is a second side view thereof;
FIG. 7 is a top view thereof;
FIG. 8 is a bottom view thereof; and,
FIG. 9 is a rear view thereof.
The evenly-dashed broken lines of FIGS. 1-9 depict portions of the seatback holder for objects that form no part of the claimed design. The dash-dot-dash broken lines of FIGS. 1-6, and 8 between the solid line portions and the broken line portions of the seatback holder for objects depict the boundary of the claimed design and form no part of the claimed design. Portions of the seatback holder for objects shown in dashed lines beyond these boundary lines form no part of the claimed design. The seatback and the object illustrated with evenly-dashed lines in FIG. 1 illustrate an environment in which the seatback holder for objects can be used and form no part of the claimed design.