Don't think there is any camping there. North to Boyne River or south to Granite Crk are closest if you're looking for free spots on the Bruce.

I concur with dabbler - no overnighters at Miriam Vale unless you pay to stay. Gin Gin 100 km south, Granite Creek about half way between them, Boyne River to the north and Calliope River north of that. Boyne River is the smallest so you may not get a spot if arriving too late - all the others have plenty of room.