We will be taking the train between Messina and Palermo in December. We are looking for an good place to stop for a night or two. We have stayed in Cefalu before and are thinking about Milazzo. Will not be planning to visit the islands. We’ll save that for when we have more time.
For me, it's worth exploring any coastal town in Sicily, but it might e more interesting to go south into the Madonie Mountains. I imagine you'd have to take a bus, to a town like Petralia Soprana. That area would be good in winter, I think, and you could find an agriturismo that offers the foods of that area, different from the food on the coast. That would be south of Cefalu.
This place is close to Cefalu and seems to be very popular with travelers:
You could easily spend a night or two in Milazzo, it's a pleasant town and there's a nice south facing promenade for strolling in the winter sun. The only thing to bear in mind is that the railway station is 4 kilometres from Milazzo which is less than convenient. The bus service between the station and Milazzo centre isn't that frequent and doesn't take into account train delays. A taxi is probably the best option (10 euros abck in 2017).
https://slowtravelitalyspain.blogspot.com/2019/05/milazzo-trip-report-september-2017.html
*f you do not choose Milazzo and want an environment different from that of the coast, there ice a bus from Cefalu to Petralia Soprana; the trip takes just over one hour. I had read some about this area because I was thinking of visiting after our last stay on Salina; I think the Madonie Mountains are a favorite of Sicilians on weekends and holidays. December must be mushroom, truffle and chestnut season....
https://beeseurotravel.com/is-hidden-petralia-soprana-worth-your-time/
https://www.esplora.co.uk/blog/sicily/petralia-sottana-and-petralia-soprana/
You can almost always spend a night or two in any town, especially towns in Italy.