The ornamental design for a lightingsystemsuspension, as shown and described.
FIG. 1 is a top perspective view of a lighting system suspension showing my new design;
FIG. 2 is a bottom perspective view thereof;
FIG. 3 is a first side elevational view thereof;
FIG. 4 is a second side elevational view thereof;
FIG. 5 is a third side elevational view thereof;
FIG. 6 is a fourth side elevational view thereof;
FIG. 7 is a top plan view thereof; and,
FIG. 8 is a bottom plan view thereof.
The broken lines shown in the drawings are included for the purpose of illustrating elements of the lighting system suspension and form no part of the claimed design.