It seems bigger that the standard TIE as it has a long ramp and is guarded by why ROTJ fans may recognise looking like as Emperial Guards.
Perhaps this is not a traditional fighter but a ‘fancy' travelling ship for an character that is hell bent on tracking someone down? An Inquisitor perhaps? Perhaps an Inquisitor played by Gwendoline Christie?
One must recognize that this design is merely a design, at this stage no one outside the production crew really knows if this design made it into the final film or indeed would will be flying this spaceship if it did.
Paul Rose Jr has worked as TV News Producer, Forensic Analyst, and Train Conductor, among many other things. He’s the former TV Editor for Infuzemag.com and owns more books, DVDs, and comics than most people have seen in their lifetimes. When he’s not writing articles, he exercises his creative muscle writing screenplays and acting in film and television in Los Angeles, CA.