I recommend you to visit the next cities and sites - hope that they're attractive in winter as well:

Taormina with its beautiful Teatro Greco and narrow picturesque streets.

Siracusa - Archeological area as well as the MidAges town.

the baroque towns of Noto, Modica and Ragusa

Palermo itself with the basilica of Monreale, Capella Palatina and many more.

Cefalu - pretty Greek town - never miss it!

Agrigento, especially the Temple valley.

The archeological site of Selinunte - really great one Segesta, not far from Trapani.

Erice - MidAges town, 750 m over Trapani.

And of course Isole Eolie!!! Maybe in winter the trip is restricted, but try to visit at least Vulcano and Lipari islands. There is a great view of most area from the Vulcano.

Enjoy your trip.

Alex Elbert Jerusalem Israel