In the scene, Henry Cavill's Clark Kent / Superman - newly resurrected - searches the fortress of solitude for a new costume to wear. Walking down the hall of the Kryptonian vessel, Clark passes several containment chambers containing different suits; there's an advanced-looking astronaut space suit, and in one chamber, a black and silver version of the DC Extended Universe suit we know and love. At the end of the scene, Clark stops and is looking at something that's lit in a bright, glowing, light - presumably the more colorful version of the Superman suit he wears in the final act of the film.
This scene is just one more clear suggestion that there is a better (or at least more complete) version of Justice League out there, somewhere. This scene is one that will likely feed into fan's unwavering insistence that Warner Bros. and DC Films release the Zack Snyder cut of the film, and scenes like this indicate that alternate cut may actually be worth the look.
Meanwhile, the theatrical cut of Justice League will be available on Digital HD on February 13th and Blu-ray on March 13th - complete with deleted scenes. The film will be followed in the DC Extended Universe by Aquaman on December 21st, Shazam on April 5, 2019, Wonder Woman 2 on November 1, 2019, Cyborg in 2020, and Green Lantern Corps in 2020.