
Make sure the texture is 8 bits/channel because a 16 bits/channel image can't be imported. The game supports other formats as well, but there is no reason to use another one, it doesn't matter how much your texture is compressed or even if it's completely solid or complicated, the game will convert it to a DXT format, so the final size won't be affected by anything other than resolution. The AppData folder is hidden by default, you can access it by copying and pasting the path into the file explorer, or pressing Windows + R and typing in appdata.

%LocalAppData%\Colossal Order\Cities_Skylines\Addons\ThemeEditor\ThemeTextures The folder where you should put the textures for importing is located here:


Also affects the availability of some environment-specific vanilla assets. Affects the cubemap which is visible in the water and highly specular asset reflections.
