Hi,
In the other post your were talking about Kefalonia. Kefalonia is really nice but also different in terms of landscapes, architecture, food, people, etc... so that can be a good change. In the Ionian group, I felt in love with Lefkada. A real paradise.
Also, if you liked Skiathos, you can go also to Skopelos and Alonissos. You can do something like a mini island hopping between those two. They look much like Skiathos but are far most authentic. No much to do at night but the landscapes and the excursions are amazing.
Also, an other area that you might like is Pelion peninsula. It is not an island and it is located in front of Skiathos, in the mainland. For me, this is one of the most incredible areas of Greece. As it is a combination of beaches and mountains. Really unique and amazing excursions to do.
Check
www.greeka.com/thessaly/pelion/index.htm
Also there, there is no much night life except from some really good restaurants. But the area is just amazing.