Fox has cast actor Nathan Darrow as Victor Fries (a.k.a. Mr. Freeze) for the current season of Gotham, according to Deadline. According to these reports, Fries' story-arc will follow much of the revised origin seen in Batman: The Animated Series and later replicated in comic books.
Darrow is best known for playing Sercret Service agent Edward Meechum opposite Kevin Spacey in Netflix's House of Cards. He's currently filming HBO's Wizard of Lies playing Bernie Madoff, and is scheduled to be a recurring actor in Showtime's Wall Street drama Billions.
Deadline doesn't say when exactly in Gotham's season Darrow would debut as Fries.