As part of director Tetsuya Nomura's XIII Days to go countdown to Kingdom Hearts III, he announced today that they will be putting promotional material of the art of Kingdom Hearts III around Shinjuku Station and Shibuya Station starting January 16. The art will be framed and displayed in gallery style around the station.
You can view the pictures he provided below.
UPDATE [Jan 16, 2019]: Fans have managed to get some new snapshots of the display. Thanks to sora_kai_1130, you can take a look at some of the pictures below: