There is onsite camping located outside the fenced off events area. You will need to purchase your camping ticket separately to your events ticket. There are only 1900 camping tickets sold and as the festival handles 17500 people, a majority will need to find alternative accommodation.
As the onsite camping grounds fill up quickly you may need to investigate other accommodation options. Byron Bay town has a huge variety of places to stay at during splendour in the Grass festival. Options include motels, backpackers, bed and breakfasts, holiday houses etc. For a full range of accommodation options around Byron Bay click the link the following link.