Pretty Valley Hut is probably the most popular designated camping spot on the high plains closest to Falls Creek - a bunch of folk camp out that way, including MTB. There's also the camp areas out on the high plains incl Raspberry Hill, Langford West, Buckety Plain etc. Bush camping is also permitted elsewhere, think some restrictions apply e.g distance from roads etc.
FWIW I'd be checking out Pretty Valley, great spot and it's a pretty cruisey ride into Falls and back. The lodges in the village that have sponsored Ignition are also offering special deals for the weekend.