Square Enix worked with a number of guests artists on Bravely Default: Flying Fairy. Dengeki Online posted concept art from the game like this artwork from Atsushi Okubo. Okubo is the creator of Soul Eater and he made the Valkyrie/Einherjer Venus costumes for Bravely Default.
Light novel artist Foo Midori created the mad scientist character Kada, one of the rival characters in Bravely Default, and the Chemist job costume.
Lord of Vermilion Re:2 illustrator Hideki Ishikawa created the bad guy Nicosguy Boritori and the Merchant job.
Take who did character design work for Katanagatari drew Victoria, another rival character, and the Magus job.
Makoto Tsuchibayashi a character designer for the Sengoku Basara series made the Swordmaster job and Izumi Kami.