Doodly doodle time! I've been working on this particular setting for a little while, a currently unnamed generation ship that left the solar system 3,674 years ago, however, the exact reason for departure is unknown to the general public.
The ship itself was originally equipped with 3D printers, refineries and several bio-labs and crop fields. So it has been continually added upon since departure, intercepting various asteroids for raw materials: now the ship has grown from the size of a cruise liner to the size of Shanghai.
The original passengers and crew of the ship were majority Han Chinese, with the remaining 30% coming mosty from Central and Northern South America. Currently, the inhabitants have a form of insular dwarfism, which has been selected for as a method of conserving resources. Hence, the average height is 4'4, and around 70lb. They have very little body hair (a filter-friendly engineered trait) and short dense hair. Their blood also contains elevated red blood cell levels, due to early days of the journey being struck with oxygen distribution and supply issues. A modern human would develop mild hypoxia under the atmospheric conditions onboard.
Hairstyles are short, and don't get caught on things, while no piercings are present: anything that can get hung on tunnel walls is taboo. So they use sticky faux gems.
Living quarters are very space efficient and communal, the passengers have very little personal space at home, though there are garden chambers everywhere that aren't as well trafficked. They are much more touchy than modern people due to a long term space shortage over millenia. More information to follow in another post.
The gravitational situation on the ship is really quite complex and needs a full post unto itself, but the little diagram more or less explains it.
Finally, a tiny Ryo floating away from their bed during a slowdown burn. @randomly-random-stuff discussed some of this, so I felt obliged to give a cameo.