What about sticking 2ft of trellace along the top of the fence and planting some fast growing climber's something like clematis..i made my own trellace out of several pack's of roofing lath's and it's been up for year's with no sign of rotting or falling to bit's.
http://www.vanmeuwen.com/trees-shrubs-ornamentals/climbers/clematis-winter-beauty/69519VM