I claim the ornamental design for a ceiling fan, as shown and described.
FIG. 1 is a front perspective view of a ceiling fan showing my new design;
FIG. 2 is a front elevational view thereof;
FIG. 3 is a rear elevational view thereof.
FIG. 4 is a left side elevational view thereof;
FIG. 5 is a right side elevational view thereof;
FIG. 6 is a top plan view thereof; and,
FIG. 7 is a bottom plan view thereof.
The broken line showing of the ceiling fan canopy and support pole is included for the purpose of illustrating environmental structure and forms no part of the claimed design.