The ornamental design for the wall mount support, as shown and described.
FIG. 1 is a top front left perspective view of the wall mount support with the front cover plate removed;
FIG. 2 is a front plan view of the wall mount support shown in FIG. 1 with the front cover plate removed;
FIG. 3 is a rear plan view of the wall mount support shown in FIG. 1 with the front cover plate in place; and,
FIG. 4 is a left plan view of the wall mount support shown in FIG. 1 with the front cover plate in place, the right plan view being a mirror image thereof.