Hey y'all. I'm homebrewing a new campaign for my crew after our first finishes. The new world is going to have 8 elemental types, but is only going to have humans. As such, I want to come up with a trait for each element that works that the PC gets at level 1 when they pick their element. I have:

Air: you gain proficiency in dex saves, if you already have proficiency choose another save of you choice. 

Body: you gain a bonus 2 HP per level up.

Earth: you gain 5 walking speed, it grows to 10 at level 5.

Fire: you learn the fire bolt cantrip. You choose the spell casting modifier when you create the character

Lightning: when you are attacked you can use your reaction to deal 1d6 lightning damage to any target within 10 ft. This damage scales like a cantrip. 

Metal: you can identify and mend any man made object made of metal.

Mind: you learn the message cantrip. At level 5, you learn the sending spell and can cast it proficiency times per day.

Water: you are amphibious and have a swim speed of 30 ft.

I'm not super thrilled with the body element trait and some of the others could be more unique. Anyways just wanted to see if the community had any good ideas. I don't care as much for balance as I do for fun and thematic abilities. 

You could do Body the same way some AC calculations are done, like the Draconic Sorcerer: AC is 13+Dex, and you also gain an extra few HP per level. 

And for the Fire, if you want to go for flavor more than balance, Produce Flame is a much better "fire" cantrip. Or maybe Control Fire?

That being said, there's also Gust, Mould Earth, and Shape Water.... there's a lot of choices for elemental cantrips! Even Mind Sliver for the Mind 'element'.

I like the idea of a natural armor trait. Seems better and more interesting than just a generic stat boost. Changing the fire cantrip makes sense too. I'm actually trying to avoid just giving everyone a matching elemental cantrip. I'd like the traits to be more unique, I just couldn't think of anything better for fire. Though I guess if only one element has it then it is unique. 

So I know you said you don't care about balance, but do your players care about optimization? because they are pretty unbalanced with each other right now so if your players are optimizers I'd see most of them picking the same one or two traits that are the most powerful.

Here are some more possible options:

Air - your jump distance is tripled, as a bonus action you can move a creature that is within your reach up to 10 ft away from you, 1/LR you can summon a tornado around you that give DisAdv to all ranged weapon attacks that target you for 1 minute.

Body - when unarmoured your AC = 13+Dexterity modifier, as a bonus action you can attempt to grapple one creature within your reach, prof times per LR you can give yourself advantage on a strength or dexerity saving throw.

Earth - advantage on stealth checks to not be heard, as a bonus action you can attempt to knock one creature within your reach prone, 1/LR you can cover yourself in a layer of earth granting you 1d10+your level temporary hp.

Fire - +10 ft walking speed,  as a bonus action you can ignite any flammable object(s) within 10 ft of you, prof times per LR you can deal an additional 1d10 fire damage when you deal damage to a creature with an attack or spell.

Lightning - you have advantage on checks/saves to avoid being grappled or restrained, you can Dash as a bonus action,  prof times per LR you can deal 2d6 lightning damage to a creature that hits you with an attack.

Metal - you cannot be moved against your will, as a bonus action you can create a non-magical metal weapon or shield in your hand which vanishes after 1 minute, 1/LR you harden your skin to the texture of metal, for 1 minute all pierce/slash/bludge damage you take is reduced by 5.

Mind - you have 60 ft telepathy, you can take the Help action as a bonus action, 1/LR you can give yourself adv on Wis, Int, Cha saves for 1 minute.

Water - you have a swim speed equal to your walking speed and can breathe in water, as a bonus action you can extinguish any fire within 10 ft of you, prof times per LR you can transform into water & move through any gap as narrow as 1 inch.

Wow! I really like a lot of those. You're way more creative then I am.  I like the idea of maybe having a passive and active portion of it. In general, they haven't picked the optimal path in this first campaign, or at least haven't meta'd the picks. 

My hope for this new campaign is that they get a trait at creation and then we'll work together to add a new trait every 3-4 levels. With how they're choosing to use the element playing a bigger part in how those later traits work. Kinda replacing the slot of magic items in a way. So in that way I want this first trait to be useful across all classes but not necessarily balanced against each other as I'll work to buff the people who aren't performing as well (and maybe nerf some though I really wouldn't want too). I just want the trait to be something they use consistently to help them get into character. 

That's a cool idea, then maybe start off with the passive and an active portion later.