“I got some big high heels to fill,” said Tim Williams, the new executive director of Habitat for Humanity of Hall County. He’s not exaggerating. Habitat of Hall has developed one of the more stellar reputations of any local nonprofit thanks in many respects to the leadership of Ann Nixon, who has taken the organization over the last four years through its biggest and most successful period of growth — including the acquisition of the Copper Glen subdivision off Baker Road near Ga. 60/Candler Road where Habitat is developing 21 homes, plus a walking trail and community garden, on 42 donated acres.