GalCiv II is extensively moddable.
Everything in the game is in an open format of some kind. Screens can be modified with DesktopX (www.desktopx.net). The models are .X files, the graphics PNG and the data XML.
One user, Winterlight, has already figured out how to put in his own .X files.

Look closely at the ship since it's not textured. There's no polygon limit in GalCiv II.
Most games tend to start to look dated because they limit how many polygons they can do in their models. GalCiv II has no limit, your system performance is the only limit. So there's no limitation on how big your textures can be or how detailed your ships except your own system performance.
This was done so that the game can be kept "new" for years to come.
The post that discusses that Bird of Prey can be found here:
https://forums.galciv2.com/?ForumID=162&AID=102652