I'm going to stick with the OPs premise of 'Little Things' I'd like to see, because I've been posting for Years about Big Things I'd like to see . . .
Reflect the continents on the map.
This would, in a way, hark back to the differentiation of the continents in Civ 5, but with a major difference: it would not be limited to color of foliage, but include actual landform appearance. This would be a much more variable map visually, but the actual effects on game-play would not necessarily be that much more than in Civ currently.
Chinese steep tree-covered mountain peaks
Rocky Mountain hanging valleys, box canyons, granite peaks
European Dolomite-like rocky cliffs
Sand dunes like the Sahara
Rocky plains like the Gobi
Dramatic Mesas as in the American Southwest
Frequent bright colors in cliffs and peaks.
Division into Coniferous, Deciduous, dryland, Rain Forest, Taiga.
Dryland could be coniferous ‘lodgepole pine’ as in the American West OR
Deciduous scrub oak as in Tunisia/North Africa
High latitude deciduous would combine marsh, massive oak and hemlock and maple
High latitude Coniferous would segue into Taiga
Rain Forest would be mostly heavily-vined tropical with perhaps one example of a Temperate Rain Forest of giant trees (red cedar, Redwood, Sequoia)
Forests next to or near Cities would automatically be ‘cleared’ or cut down early in the game unless stopped by building a Special Something on it, like a Sacred Grove, Hunting Preserve, etc.
The new “grassland/plains’ of Civ: Tall Grass, Short Grass, Savannah (scrub)
Animate more of the map. Railroads should have trains, and the trains should start out as little wooden cars and steam locomotives, progress to steel cars and big steam locomotives, then to big steel cars and diesels in 'unit trains'. Caravans should, as others have posted, reflect their geographical/climactic origin: mules and donkeys were the most common pack animals, then camels one and two-humped, yaks and lhamas in high mountains. Have carts and wagons on the roads around the cities, later upright chugging Model-T-type cars, finally big trailer trains and SUVs.
Don't be afraid to show the Dark Side of cities: smog and soot overhead, grimy run-down buildings around the Industrial/warehouse/harbor areas, maybe even people moving out as refugees when things get Really Bad.
Individualize My Game:
Let me name Everything on the map: Mountains, Volcanos, Mountain Ranges, Rivers, swamps, bays, marshes, lakes and seas, etc.
- And then rename them later if I control them.
- And that should include Wonders and even Districts: why can't I have the Detroit Arsenal or Vickers Armstrong Works in a city, or the Helios instead of the Colossus?
Let me change the name of the Civ and Leader. If I want to play as Asterix the Gaul instead of Ambiorix or play as Greater Slobbovia instead of Armenia, that should be My Choice.
And from the start, be able to name/title any and all Units, from Tribe to Battleship.