Gracie already is a nickname.
Famous people named Gracie:
Gracie Allen, comedian and wife to George Burns; classic English actress Gracie Fields; American figure skater Gracie Gold; daughter of Faith Hill and Tim McGraw.
Gracie is the name of many well-known fictional characters, including Miss Congeniality herself, Gracie Hart. There are characters named Gracie on CSI, The Nanny, and Friday Night Lights.