There are tons of things you could mention - Mr Birling is a point goldmine.
One interesting idea you could mention is how Priestley presents Mr Birling. Mr Birling is presented as an idiot, which is very obviously broadcast to the audience within the first few minutes when Mr Birling makes a number of clearly wrong statements (like the Titanic is the greatest ship ever made and is unsinkable, and that the "Huns don't want war", both of which are incidentally examples of dramatic irony). Bearing in mind that Mr Birling is a symbol of capitalism in An Inspector Calls, you could argue that Priestley is making a statement about what he regards capitalism (or capitalists) as through the characterisation of Mr Birling.