Above is the cover from the new Blizzard/Dark Horse Overwatch graphic novel. The 100 page book will tell the story of the original Overwatch strike team. Depicted in the image are Reinhardt, Torbjörn, Reaper, Soldier:76, Ana Amari and 3 other characters who remain unknown (at least to me). The first appears to be a type of mech (possibly a front-line omnic), the second is an omnic more similar appearance to Zenyatta and the third (who could possibly be Sombra) is a young girl sporting glasses. The character gives off a hacker vibe to me and we know that Sombra has a pre-exsisting relationship with Reyes.
Let the theorizing begin!
UPDATE* Nvm, pretty sure it's the previously unseen founding member Liao. Still interesting stuff.