Fabio Fognini was fined US$3,000. The Italian said during his third-round loss that he wished a bomb would hit Wimbledon.
Nick Kyrgios was handed two fines, one for US$3,000 from the first round and another for US$5,000 from the second round both for unsportsmanlike conduct. The Australian lost to Rafael Nadal in five sets in the second round.
Williams' offence took place on one of the outside courts, which players are allowed to use for training before the championships.
Earlier on Monday (Tuesday NZ time), Williams eased into the Wimbledon quarterfinals for the 14th time by beating Carla Suarez Navarro 6-2, 6-2 on No 1 Court.
Williams won six straight games from 3-2 in the first set to take control of the match. She raised both arms in celebration after her fifth break of the match gave her a 5-2 lead in the second set and served out the victory when Suarez Navarro sent a backhand wide.
Williams is looking for her eighth Wimbledon title after losing last year's final to Angelique Kerber. She has never lost a set in seven career meetings against Suarez Navarro.
Williams will next face fellow American Alison Riske, who upset top-ranked Ash Barty earlier in the day.