Hi there, it's all the same site, with different frontends. Think of Hive as the house, and there are different doors (frontends) to access the house eg hive.blog, peakd.com, 3speak, ecency, LEO Finance. Whatever content you post from these frontends will all end up on the same Hive blockchain. You can use the same posting key to access all the frontend.

I don't personally use 3speak so don't know where you change the profile picture. However you can change it in any if the other frontends and it will flow through. I'm on peakd.com on mobile. Just click on those 3 little dots next to setting to do it.