The SFB pained T'Korex has been upgraded to a heavy command cruiser variant. You can see the addition of upper engine pods. the underside has a bridge which is not visible on this view. Here is a picture of the underside:
The bridge is more visible on this view. All the other Romulans have, except for the V'Tir light cruiser have extra components to allow upgrading. Additional pictures can be seen in the Romulan Gallery.