Re: Best way to prepare for a design interview
On top of what you have:
Prepare some questions to ask them. Eg Studio culture, team celebrations, etc?
They might ask what value you bring to company (i.e. why should they hire you)
They might give you a scenario or problem to fix/work through. Just remember to verbalise your thinking otherwise you will end with silence.
Favourite games and why. They might extend the question on to how you would improve it.
That's all I can think of at the moment.