This is all I know about the ISC races - I've seen no material relating to race specific designs (except the Q'naabian War Cruiser on which is this was based).
ISC Member Races:
Veltressai:
The Veltressai are an odd and powerful race. Once in twenty births, their young are born from a single fertilized egg that undergoes fission in two successive stages, yielding four identical children. These quadruplicates are empathically and telepathically linked and, for all intentes and purposes, are four extensions of a single group mind. Any information or experience known or felt by one of the four is relayed telepathically to the others and is part of their common experience within minutes. This telepathic/empathic ability. while slightly variable within the race, may never exceed a range of 25km. They have a memory buffer which allows them to function as one of four separate entities, while still mantaining peripheral contact with the other three. The Veltressai are often called the Captain's Race. This is because while one is on the bridge, the others can be sleeping, conducting inspections, etc. It is like having the same officer constantly on duty!
Pronhoulites:
Pronhoulites are distanly related to both the Gorns and the Hilidarians (Klingon subject race). They are reptilian humaniods who come from the same stock that is believed to have become extinct on Earth with the passing of the dinosaurs. Pronhoulites are a land-based bipedally erect race. They are notas physically powerful as the Gorns, but are much faster. Pronhoulites are not technically advanced or numerous enough to becomae a major power in known space in the near future. They are agressive, adaptable, and very adept at military matters.
Q'Naabian:
The Q'Nabbbians are an enigmatic race, having joined the ISC more out of a sense of curiositiy than from a desire to improve or protect the galaxy. It is rumored that they are the historians of the ISC, responsible for the recording the exploits of the ships they serve on. They tend to keep to themselves, giving the other ISC member races the impression that they consider themselves superior. In fact, they simply prefer the company of their own race in their environmentally controlled, oxygen/chlorine atmosphere cabins.
Rovillian:
The Rovillians are a psionically active aquatic race that look like a cross between a turtle and a dolphin. They have vestigial exo-chitin on their backs and heads and possess crudely articulated digits on their flippers.
Korlivilar:
The Korlivilar are a feline race similar in general appearance to the Kzintis and the Lyrans.