According to
SEnet:
Like SEIV, the SEV vehiclesizes file defines primary and alternate model/texture files for each hull. In addition, it also defines a default, thus allowing for 3 possible file specifications. The file is set up to support the following additional models for ambitious shipset authors:
LightCarrier
HeavyCarrier
Baseship
Small, Medium and Light verisons of: Freighter, Drone, Fighter, Mine, Satellite, Troop, WeaponPlatform
Another thing to note is that the Organic and Crystalline racial traits in SEV provide specialized vehicles hulls. There are calls for specialized models and textures for every one of these vehicles, so a very ambitious shipset author could provide different textures in an "Organic" style for Organic races, for example.