Here is a design sketch I've been working on since yesterday morning. It's the Strategic Space Command warship Ninegal - currently called a General Deployment Vehicle (GDV) but I'm considering alternative designations. The total length is around 2100m.
From front (left) to back, the sections are:
- Command
Habitat
Water
Power Plant 1
Exotic Geometry Motor
Power Plant 2
CHON storage
Cargo
Newtonian Motor
And those are radiators, not solar panels. The probably need to be re-sized depending on the actual peak output of the nuclear powerplants and the gross heat-bleed from the Exotic Geometry Motor. The Newtonian motor is probably a VASIMIR, since you would want to maximize the ΔV of your backup motor rather than its maximum thrust.
This sketch is missing a lot of vital parts, however. I have not allocated room for a primary laser, nor docking for scouts, shuttles, combat drones, or missile buses. A ship like this will need all of those things.
For comparison, see this Logistics Support and Command Vehicle:
I forget how big this is . 600m?
It basically started when I wanted to crop one of my pictures and I was looking for how to do that (...you can tell I use the program a lot to edit photos 
...I mean, it's Windows Photo Gallery, you're just supposed to look at pictures!), and then noticed "oh hey, wouldn't it be funny if I just adjusted the colors a little bit?" and then kind of exploded all over the pictures. Some of them turned out cool (Summer Palace, and I also like the sunset ones and the Shanghai skyline), some of them not so much (the soldiers, and the hutong one looks strange, I think)
What software do you use?
