Wilderness is essentially trackless country with no signs of human activity - something becoming increasingly difficult in our over populating planet. All traces of a fire built over a sand base can be completely removed. No scorched rock or ground, nor ashes is the way you found it and the way the next person would like to find it.
The area has much Aboriginal rock art and sites of significance. You shouldn't light fires or camp within these sites. Objects or art shouldn't be touched, moved or otherwise disturbed. It's a matter of respect for the property and culture of others.