The ornamental design for a ceiling mount, as shown and described.
FIG. 1 is a perspective view from below of a ceiling mount in accordance with my design;
FIG. 2 is an enlarged perspective view from below of the ceiling mount in accordance with my design;
FIG. 3 is an enlarged side elevation view of the ceiling mount in accordance with my design, the opposite side being a mirror image of that shown; and,
FIG. 4 is an enlarged top plan view of the ceiling mount in accordance with my design.
The broken lines showing environmental structure are for illustrative purposes and form no part of the claimed design.