In Star Trek, pretty much every single human-designed ship we've seen is a Starfleet ship. As such, I assume they all have standards, go through essentially the same review process, and probably see much of the same designers working on them throughout the years, hence why through each era, ship designs look at least halfway the same.
In the civilian market, however, I can see competing manufacturers designing their own breed of ships, though they still have the futuristic, largely human designed, ship designs. Though Picard said there was no money in the future, this seems to be contradicted by DS9 and such, so I'm making the assumption that the civilian economy is still market capitalism based.
So, if you guys have ideas for civilian human ships, any era, I'd be interested in seeing them, because civilian life is something that can be greatly expanded upon in the Star Trek universe.
I'm going to focus on TNG/Nem era mostly, and I'll probably have some ideas up soon.