Helnic, if you are travelling via the coast road, in Cairns there is the Lake Placid Top Tourist Park 07 4039 2509 and Cairns First City Caravilla Park. The later park has quite a large area for storage, and usually has a lot of vans in storage.
We left ours at Mareeba Country Caravan Park. No charge for leaving in storage, left ours there for 6 weeks. Stayed 2 nights either side of our trip up. Those nights were $25 per night. They figure travellers would spend a few nights either side of their trip, and make money that way.