Part of the "Megastructures: The Visual Encyclopedia" book project, on sale now at https://www.kickstarter.com/projects/artofsoulburn/megastructures-the-visual-encyclopedia-book-project.
One of the main needs of a space habitat’s population would be food. While many habitats could reserve internal areas for farming, farmlands could also be attached to the habitats in connected structures. Other options would include internal food production such as vertical farming, or creating exterior movable platforms, like floating farms in space.
Zero-g plants would be placed on the platforms, with enclosures to retain atmosphere. A highly controlled environment would mean factors such as temperature, humidity, soil, light, and atmospheric gases could be customized specifically to achieve the highest crop yield, which would be harder to achieve in a mixed-use situation where crops and human populations coexisted inside a single habitat.
Lighting could be artificial inside the platforms, or a set of mirrors could be used that would reflect real sunlight, creating a fake day/night cycle. Seasons could be simulated as well.
As a population grew, more of these floating islands would be created and added to the cluster. Giant tug robots could move the islands to new locations, or even bring one back to the space station for repair, or at harvest time to unload its yield. The farms could be entirely automated with robot gardeners, or have a small population of humans looking after the crops.