It's very hard to see, but the images below are being said to possibly be a new Mortarion. This is quite hard to believe at this point, but it's worth taking a look at.
Please remember that this is a rumored image. Please give it plenty of salt right now.
via Ishagu on Bolter and Chainsword
Sharing this bit of juicy gossip.
The next Traitor Primarch is going to be Mortarion. Winged, same scale as Magnus.
Here is the source of the images for the discussion along with the image below.
They may have originally been posted up on 4chan.