It can be hard now for backpackers/visitors with only a vistor visa. There is normally work in vineyard areas in Victoria and SA after Christmas, but very little fruitpicking along the Murray Valley because of water restrictions. One backpacker who stayed recently with us for hospital visits, had come from the Ord River area, and had plenty of work there picking pumkins, melons. He and his friend had worked for cash on a station nearer Perth and were grossly underpaid, but in cash - I think they were "had" ie exploited.
If you have experience with driving tractors and harvest equipment, there is normally work from now until March from Queensland to Victoria.