So recently I've started creating doing what I've called "Model Train Worlds" that are settings and characters that I would work on to blow off steam for fun, practice writing/worldbuilding, and general test out ideas even if I never publish anything from them proper. It's been fun to fiddle with and experiment with these types of settings.
One of these "Model Train" worlds I've been thinking of working on would be one inspired by LEGO's "Elemental robots bumbling around an alien planet" type stories like Bionicle, Throwbots, Roboriders and (Kinda-sorta) Hero factory. (Would Ninjago count as a pseudo successor to that type of stories given that it's elemental ninjas bumbling around a fantasy world?)
Anyways, I wanted to have a group of elemental characters/Environments/tribes for this setting, but I don't want it to be a 1 to 1 copy of the elemental sets of the prior inspirations (Fire, Water, Ice, Earth, Plants, Metal, Air, and Electricity/Energy for Throwbots. Fire, Water, Ice, Air, Earth, Stone, Light, and Shadow for Bionicle's main ones. Fire/Magma, Plants/Water, Sand/Air, Earth/Rock, Ice, and Metal/Energy.) I know I will have the classic "Fire, Water, Jungle, Ice, and some form of Earth related" Biomes in my world, but I want to be a bit more original than just copying the above listed elements wholesale.
So what are some unique elements would you add onto the classical ones and which comibnation of six or eight elements would you pick if you were tasked with building such a story/world and why?
Thanks for the help and I eagerly await your answers. 