Tjaynera Falls is amazing.
In Litchfield so easily accessible for a day trip, it has rudimentary camping facilities, though I have never stayed there.
It is down a 4WD track that is moderately challenging, you need to cross some water.
The bushwalk is moderate when you get there it is definitely worth it.
A great waterfall that flows all year round, a great swimming hole, and usually only a handful of people.