I claim the ornamental design for a display module, as shown and described.
FIG. 1 shows a front view of the display module;
FIG. 2 shows a left side view of the display module, the right side view being a mirror image thereof;
FIG. 3 shows a top view of the display module, the bottom view being a mirror image thereof; and,
FIG. 4 shows a rear view of the display module.
The display module, suitable for displaying energy usage information or other data, may utilize liquid crystal (LCD), electroluminescent, vacuum fluorescent, LED or other display technology allowing selection of which elements of the display surface are visible and which elements are not visible at any given time. The broken lines showing certain display elements, the bezel and case are for illustrative purposes only, and form no part of the claimed design.