I found a link at the Ministry of Foreign Affairs:
I want to stay longer than 90 days (MVV procedure):
An MVV is needed by the nationals of all countries except the EU member states and a few other countries.
Australia is listed as one of this countries:
Countries whose nationals do NOT require an MVV for a stay of more than 90 days
I would recommend to ask the embassy to be sure about this.
Maybe you can attend a university and ask for a student visa.
But the Student visa wizard also confirms for Australia:
You do not need a visa to enter the Netherlands, neither for a short, nor for a long stay. All you need is a valid passport.
I found another interesting website http://english.ind.nl/residencewizard/ :
For holidays longer 3 month I found the information:
Holiday longer than 3 months
It is not possible to apply for a short stay visa for a period exceeding 3 months. If you wish to stay in the Netherlands for longer than 3 months, you must apply for a residence permit. In order to be eligible for a residence permit you need a purpose of residence other than holiday and you must meet the conditions of the purpose of residence you have stipulated.
Perhaps you find more informations there.