Hi Kat,
the number one thing to remember about EngLang essays (or any essay to be honest) is that evidence and examples are crucial in supporting your point, and can often be the difference between a 'B' or an 'A' essay.
In terms of AusE and Identity, I think a really good example (in addition to what Bri said) is any form of promotional adverts (eg. TV, Radio, newspapers or billboards) that feature in the Australian mainstream. For example, McDonalds ran a promotional activity in January 2019, in the lead-up to Australia day where they put up billboards with lexis emulating the typical connected speech processes that are akin to the 'Aussie' broad accent (eg. Qwarter Pownda). You could argue that since McDonalds aimed this promotion at the Australian public, they are attempting to align themselves with favoured conventions, thus informality is seen to be accepted due to Australia's egalitarian values. However, this is one interpretation of that example, you could take a few others with it.
So, whilst you couldn't use that one specifically (must be 2020 onward for the exam), look out for such promotions (eg. Australia Day ads, more company adverts etc.) and pepper them into your essays. That's only one form of 'informality' too. I'd highly suggest looking into other examples such as the 'views on and use of profanity in Australia' (google 'Yahya Tuameh' for a great example of that one) as well as any form of sociolect, including ethnolect use in Australian society. Indigenous Languages are another great one, albeit less prevalent, however I found an example and used it in my exam, and I honestly think it saved my essay.
Hope this helps!