In the DC Comics, Elinore Stone is the mother of Victor Stone, aka Cyborg, and works as a teacher and scientist at STAR Labs, and is also the wife of Dr. Silas Stone, who is played by Joe Morton in the Justice League movie.
We can guess that with the addition of Karen Bryson as Elinore Stone that they will be showing more of Cyborg's back story and origin in Justice League as the same accident caused by Silas Stone that turned Victor Stone into Cyborg also killed Elinore Stone (at least in the comics). Hopefully this also means they are developing Cyborg's character to lead into the solo movie.
Karen Bryson is known for the Shameless and Cuffs TV series.
Justice League has a November 17, 2017 release directed by Zack Snyder, with the story by Chris Terrio and Zack Snyder, the screenplay by Chris Terrio and Joss Whedon, and stars Ben Affleck as Batman, Henry Cavill as Superman, Gal Gadot as Wonder Woman, Jason Momoa as Aquaman, Ezra Miller as The Flash, Ray Fisher as Cyborg, J.K. Simmons as Commissioner Gordon and Willem Dafoe an Atlantean, Nuidis Vulko.
Fueled by his restored faith in humanity and inspired by Superman’s selfless act, Bruce Wayne enlists the help of his newfound ally, Diana Prince, to face an even greater enemy. Together, Batman and Wonder Woman work quickly to find and recruit a team of metahumans to stand against this newly awakened threat. But despite the formation of this unprecedented league of heroes—Batman, Wonder Woman, Aquaman, Cyborg and The Flash—it may already be too late to save the planet from an assault of catastrophic proportions.