Our great Community crated multiple Mod's for Techtonica as well as an additional Mod-Loader.
You can find detailed informations about the mods in the official Discord and you can additionally download them directly here:

MOD-Collection at Thunderstore: https://thunderstore.io/c/techtonica
MOD-Loader: https://github.com/CubeSuite/TechtonicaModLoader/releases

Please keep in Mind:
Mod's are not official supported from the Game Developer FHG, so use them on your own Risk!
Always its recommended to create a backup of your Savegames before using Mod's.
You can find you Savegames here: %APPDATA%\..\LocalLow\Fire Hose Games\Techtonica