A commonly-forgotten fact about the western-element system is that it is not, as media commonly portrays it, actually a four-element system. The western element system we are familiar with has a fifth element, a "heavenly" element, Aether/Ether, the element of the stars, what the heavens are composed of. But I'll talk about that more in a bit.
The "worldly" elements were the four elements making up the world: fire, water, air, and earth. We all know the four-element chart. Water, opposite of fire; Air, opposite of earth; Water beats fire beats air beats earth beats water is often also used. There's so many things about this system which are commonly seen. It's a pretty standard system, subverted plenty of times, and people often "get creative" by later introducing a 'fifth element' of their own (which is usually something completely different from the original fifth element but not necessarily!).
I'm not quite as familiar with the eastern-element system, but they also use a five element system. I believe their traditional system is Fire, Earth, Metal, Water, and Wood. But coincidentally, at least in my own elemental creativity, I will be talking about those later, too.
The next step up is the eight-element system. It keeps Fire, Water, Earth, and Air, but adds Light, Dark, Ice, and Energy to the spectrum. This also has a side-effect of changing elemental dynamics. Water gets paired with Energy; Fire gets paired with Ice. Because eight elements are more complicated, there's a lot more diversity and interpretation in there. Do you have a wheel on elemental affinities (i.e., one element beats another but is beaten by a third)? The possibilities are far more diverse than with only four.
This is the system I tend to most commonly use, thanks to my upbringing in Artix Entertainment's first game, Adventure Quest. It was what I used in my previous webcomic (speaking of which I made art for that today!), and it's what I use in Red Hood Rider, too. I like the eight-element system because of the incredible flexibility it provides. A four-element system gives you access to some creative ideas (for instance a favorite of mine is, "four elements, four fundamental forces of the universe"), but an eight-element system just feels a whole lot more ~official~ I suppose it would be, in that when I have it I feel more grounded in reality. It provides the best balance between having a lot and having a little, because once you expand beyond eight, there's no limit to what you can give.
For instance. The obvious step up from eight is the ten-element system. Generally the simplest and easiest way to get a ten-element system is to subdivide the Earth-element. (You can blame Bionicle for what I ended up with.) You can subdivide it into any number of different things, but I have a preference for these three:
-Metal
-Rock
-And Nature.
Included in Nature would therefore be Wood. The reason I like these three is because these three are all relatively broad, yet common, elements which encompass essentially everything Earth has to offer. Metal is everywhere in our world. If Metal is not classified as its own element, it's under Earth because where else would it go? It's not fire, it's not ice, it's not energy, it's not water, it's not light, it's not dark, it's not air. It's either a part of Earth, or it's its own element.
Avatar: The Last Airbender may have popularized the idea of metal as an element (at least a sub-element of earth), but the idea has been around since long before then. It makes sense, after all. The explanation given is usually to the effect of what Avatar gave, in that metal is just refined rock, but I like to separate metal and rock.
Rock is what covers a significant portion of the Earth, too.
And Nature is what makes up life. I tend to not call it Life as an element (because that itself can be an element, but see below), but the sentiment is there: it is both flora and fauna, in that it is everything organic, more or less, in the world. It WOULD be possible to subdivide it in half, into said flora and fauna (making it basically be Wood / Nature as two separate things), but this is not something I often do.
...However, something I DO do? Often, if this still feels too narrow--and it usually is--instead of not including an element named Earth, I will include an element named Earth, which would be the broad sweeping category of "everything on the planet (more or less) not fitting into one of those three categories". If sand/dirt don't count as Rock, they'd count as this version of Earth. Things like poison, acid, gasses which aren't classified as air, and the like would also fit into here.
We're up to eleven at this point.
Then comes the biggie category. Spirit/Soul, Aether/Ether, Heart/Love/Life, Heavens/Stars/Divinity/Holy, Ethereal/Dream, Ki/Chi/Xi/Chakra/Body Energy. You can potentially get 10-12 elements from these, or you could lump them all into one element of your choice name. They cover similar concepts which is why I lump them together, but they are not in fact synonymous. I tend to separate them out into about two (maybe three) categories: "heavenly otherworldly element", and "material otherworldly element"/"earth otherworldly element".
That is: I create one element which is an element that exists outside of the normal plane of existence, on a level associated with divinity. Spirit/Soul/Heavens/Stars/Divinity are the likely candidates for the type of name I would give that element, in that it is something on another realm and that realm is higher.
I also create one element which exists outside the normal plan of existence, which is otherworldly, and yet closely mirrors and is very directly tied to our world. Think like "The Force", or similar: something which is likely to exist in most things (or at least most living things if not). This can be Spirit/Soul/Aether/Ether/Heart/Life/Ethereal/Dream/Body Energy/Ki/Chi/Chakra.
...But often, that won't quite be adequate enough, in that you can have a need to explore something which is neither of those and yet still doesn't have a negative connotation associated with it. Something which is often considered stronger, but isn't necessarily so, in that it is an element that is necessary for the others to exist and yet it is not something superior in of itself. Soul/Heart/Life/Dream/Ethereal are the most likely candidates for this element.
Of course. There is an element that can go as far back as being the ninth element. Ninth, eleventh, twelfth, thirteenth, fourteenth, or fifteenth by this point. This element is one of my most common elements. It is, simply put: Void. Void is my staple element once I expand outside of the elemental-eight. With an eight-element system it gets lumped in as part of Darkness but the moment I free myself of that restriction, Void is in as one of my elements.
Void is an otherworldly element, yet it represents more of "nothingness" than it does "something". If I have just one between all the words I gave above, this is a binary relationship in that void is the opposite of that one. But if I have more than one, it goes something like this.
The more divine/heavenly one can be thought of as "purity of thought", more or less. The more earthly one can be thought of as "pure potential". The third would be more "purity of existence". The void, in essence, is "purity of absence". It is most strongly a counter to the first two in that it is not strictly speaking tied to death (though if death is not an element, it is likely under the realm of Void), but it is tied to the nothingness associated with a purity which stands in contrast to them.
Nothingness is itself a potential element, but it's not one I'm going to include in the list. Instead, making the list in spite of it being tied to body energy/heart/life among others, is Blood. When I expand my element system beyond the eight given, blood is often among my list, because blood serves a purpose and has a great versatility within it.
Fire, Ice, Energy/Lightning, Water, Light, Darkness, Air/Wind, Earth, Nature, Metal, Rock, Void, Blood. And then we get to choose how many of those otherworldly elements we use. At least one, with three being what we want to max out on. Which would give us a nice comfy 16-element system. This could be worked down to 15 by scrapping one. It could be worked down to 13 by two of {scrapping the second and leaving only one, combining blood with one, combining an earth element}, if I did my math right.
But this is where I tend to draw the line. 13-16 elements is about as far as I'll go. You can go further, of course. To pull up a TVTropes list of commonly-used elements (when I say 'just earth', btw, I mean "earth or an element which in an 8-element system would be part of earth"),
-Storm (I have no clue but it's not really an element)
-Gaia (just earth)
-Machines (really just use Metal)
-Crystal (just earth)
-Death
-Poison (just earth)
-Lava/magma (seriously it's just fire)
-Sun (it's just light)
-Sound (mostly just air though this is a serious contender for its own element)
-Radiation (just earth)
-Magnetism (just energy)
-Smoke/gas/mist (air or earth)
-Explosions (mostly fire with maybe some air butyeah definitely not an element on its own for me)
-Mud (just earth)
-Hellfire (just fire will do nicely thankyouverymuch)
-Illusion (neat power, but not an element)
-Time
-Space
-Gravity (strong power but not in of itself an element--it's something some elements may control though)
Some of these are things that I can probably flesh out more, but basically, most of them are covered already. You might note looking at the list that I left some off, but that's because the ones I left off were ones which had names I didn't use but were describing things I already have used.
I'm content with my little expansion, though I think I should off of an expanded-element system list what each element would actually do. Ah well. Some future blog I suppose.