The ornamental design for a decorativeportion of a ceiling fan, as shown and described.
FIG. 1 is top perspective view of a decorative portion of a ceiling fan showing my new design;
FIG. 2 is a bottom perspective view thereof;
FIG. 3 is a right side elevation view thereof, the opposing left side elevation view thereof being substantially the same thereof; and,
FIG. 4 is a top plan view thereof.
The broken line showing of a combined ceiling fan housing and light fixture is included for the purpose of illustrating environmental structure and forms no part of the claimed design.