Australia is in many ways not the typical cycle touring country, which on the other hand makes it interesting nevertheless. Outside of the costal area between Adelaide and Cairns distances between places are often just gigantic and often water and heat are the main problem.
The biggest plus is Australias nature, the fantastic wild life and the possibility to always find good camping options.
The climate is very extreme and it is most important to be at the right place at the right time.
There is everything in Australia from the very busy main road to the most remote and extrem track where you won't find anyone else for weeks. You are very easily on a very remote road. Australians themselves have far more respect of those routes and often complain about how foreigners take those roads without much preparation and then getting into trouble.
Best as always is to ask locally about the current conditions as many of the tracks in the outback periodically get closed down after bad weather.
There are a couple of long distance mountain bike trails. If I write that they can be cycled with a touring bike, I am not referring to a road bike but something made for dirt roads.
You always find a spot to camp in the bush. In the south east there are many national parks where there is mostly a camping option.
Depending on where you are this is one of the most important points to consider. Distances between shops can be up to 700km and between places with water up to 300km, so plan ahead!
Some of the best route info for Australia you can find on cycle trails Australia.