The ornamental design for an indicatorlighttower, as shown and described.
FIG. 1 is a perspective view of an indicator light tower showing my new design;
FIG. 2 is a front view thereof.
FIG. 3 is a side view thereof.
FIG. 4 is a top view thereof; and,
FIG. 5 is a bottom view thereof.
The broken line showing of additional segments of the design is included for the purpose of illustrating portions of the “article” and forms no part of the claimed design.