Recently, I happened upon some scratch built models on the blog Tempests in a Teapot and it all came flooding back.
These ships miniatures were lovingly scratch built to represent the ships from a strategy board game called "Imperium". I had this game as a kid and, while it was a bit over my head at the age I owned it, I recall adoring the evocative ship silhouettes on those cardboard counters. Imperial ships were round and imposing, looking to be full of menace and power, while the opposing force was made of sleek ships that looked like the Cold War era supersonic designs - all delta wings and conical noses.
I was inspired by this find and my love of these old designs along with others I had seen in Traveller and Battletech's expanded universe of dropships and jumpships and even the designs of Steve Galacci's "Erma Felna EDF" that appears in the Albedo Anthropomorphics (http://leadpeople.blogspot.com/2009/09/albedo-anthropomorphics-spacecraft.html) anthology comic of hte 80's.
With a ready supply of collected junk and hobby craft supplies, I set to putting together some shapes that looked right as ships of differing classes. This is just the beginning. The next step is to find detail bits that I have in enough abundance to replicate across multiple models. If parts fall short, then I will fall back on the time honored idea of class variations.