Blackburn State Park really isn't a state park anymore as it was shut down back in the 70's or 80's. There has been talk of late of Lumpkin County taking over the park and developing mountain bike trails here. This would be a great area to create a trail system for beginner to intermediate riders, as the Bull Mountain trail system is really pretty advanced.
At the present time, there are still some old trails and gravel roads on the property that are rideable. There is a doubletrack trail called the Pioneer trail that is actually pretty enjoyable, and there are numerous gravel roads going every which way.
If the area was to be developed, the possibilities would be endless!