Figuring Out Scratch Built Fleets

So, my initial brainstormed ship shapes are done. I tried to think in terms of conventional ship classes from Battleships down to escorts.

I now need to decide how I want to detail these. This is a tricky step as I have to find details bits that can be replicated. Beads and bits of sprue are the normal route for these sorts of things. 

I also need to decide what period details I want. Do I want large dish sensors or spheres? Antennae?