I made a mistake while creating my sorcerer (didn't see the option for choosing/naming familiars) - so I'm stuck with a useless familiar I don't want. Is it possible during one of the level ups etc., to change/choose new familiar (like you could do as a ranger in NWN 1)? Or possibly change it via the console?

Not that I've seen. My Druid was stuck with a fairly useless animal companion - with a bad name - for his entire career. Plus, NWN-II has gotten rid of some of the better familiars (i.e; Panther). It makes me sad.

~ Cheesegear

Familiars don't do anything in NWN2 combat wise, but when they are summoned they provide your character with stat increaces (the pig gives you a +3 to Diplomacy).

I liked the panther from NWN 1. It was actually a good help in combat, tanking for my arcane archer.

That's disappointing to hear. :( I really enjoyed my familiars in NWN1 and I almost always chose characters that could have one. I usually chose the panther as well.