Alliance are a serie of different mods. On the Star Wars GC, you can play the civil war Empire vs Rebel era + Black Sun and soon the Republic and CIS.
People asked where you could find this unit. These too images from the game art shows clearly what it was.
About the ship, I have added it for three factions, Imperials, Hutts and Rebels. It will be one thing similar to a advanced Venator. Because probably it is the other ship more closed to this.