In the current version of the game (0.0.50.5) it is possible to edit some features, both aesthetic and functional. The following information are some possibilities confirmed after testing and information from the devs.
Modpacks, as the name says, are packages of modifications made to game files. In the same modpack, it is possible to make changes to the game's sounds and music, textures, shaders, game mechanics, among other aspects. you can have many modpacks, provided they have a different name, but can only load one at once. The active modpack can be changed in the main menu.
Modpacks are an open (not compressed) folder, with the same folders inside as the New Cities steam folder (excluding the modpack folder). Any files in their proper place will be loaded instead, provided that modpack is selected in the game's modpack menu. Modpacks do not need to contain every file; only those with changes. To make a new modpack, simply copy the "yours" folder and change the name. The name of the folder will be used as the modpack name. Copy any files you wish to modify from the steam folder into your new modpack folder before changing, or you'll modify the base game instead.
LUA Constants Edit
Some aspects of the game can be changed by modifying the file "constants.lua". The file is located in "New Cities/modpacks/YourModpackName/data/constants.lua".
CStartYear = Set the starting year ingame.
Render and Camera Edit
CRenderWeather = false or true. Toggle the weather effect ingame.
CRenderSnow = false or true. Toggle the snow effect ingame.
CRenderNight = false or true. Toggle the day/night cycle ingame.
Info about the textures and colors goes here.