Nagoya Dome announced that they will be installing two large screens to complement their main screen in center field.
The current screen in center is about ten meters tall and thirty-six meters wide. The new screens will be about the same size and installed on either side of the current screen. Together, the three screens will be over 100 meters wide.
Construction will cost about one billion yen. The screens should be ready by March next year.
[UPDATE 2/21 @ 12:05am]
The new screens were unveiled on February 20.
Source: Nikkan Sports 2/20/2017