I like Saker's interpretation - she gave you a very good critique. This is a great idea for the challenge. White picket fences belong in suburbia, don't they? I always find it hard to shoot white. Your fence pops out very well here. Nice and bright!
A nice take on the challenge.. I like the angle you shot this from.. I always enjoy lines in photos.. While I like the starkness of the pure whites and blacks, I think some grays would add more texture in the blacked out areas and give more detail in the hardware on the fence.. giving this photo a broader tonal range. However, that is a personal decision and up to you as the photographer.
You were able to make what should be such a simple subject surprisingly interesting with the use of such a stark contrast. The latches, hinges, shadows, and dark grass all play so well of the bright white of the fence.