Nomads by definition are people who roam about for pasture, or pastoral tribes who largely tend to flocks of grazing animals. The geographical requirements for a culture of nomads would include plains, steppes, or desert regions, with perhaps long treks to summer or winter pasturage. Feudalism (as found in the Middle Ages in Europe), a popular cultural norm in the high fantasy genre, was a system for structuring society around relationships derived from the holding of land in exchange for service or labor. Any kingdom worth its salt would have significant geographical elements; the land would need a fort or castle which would be defensible against invaders, the land must be arable for crops, there would be pastureland for grazing animals, and there would need to be access to rivers or oceans and their ports for trade.
Arctic cultures would of course be living in areas (like tundra) where trees would either be in short supply or have evolved to survive. Food sources would be a consideration due the affect of the climate on the geography; the indigenous people could be either hunters or herders (or both, depending on the season).
Industrialized cultures also have geographical considerations. A civilization dependent on steam-based technology might be situated over aquifers or geothermal deposits. Solar and wind-based technology-dependent cultures would also be situated near geographical elements which impact the day-to-day life of the people. A civilization dependent on fossil fuels might have evolved from dependence on water power (and be situated along rivers) or wood (and located near ever-diminishing forests). And of course, a dependency on fossil fuels requires there be fossils in the first place.
