I'm building an innovative 2d platformer game, more on that later probably.

I've created basic mechanics, some basic enemies, wall jumping platforms and the like. But I just need MORE to fill my levels with.

Could you guys give me ideas for enemies, items, mechanics, basically anything(art would be appreciated, but I just need ideas)

Try to create a theme and some background story for your game. That will give you some context from which you can extract ideas. People would also be able to give you more coherent suggestions.

It's a pixel art game, where you are playing through the life of a man named Harold. You can make rpg-esque "decisions", more difficult decisions(AKA going to college) having more difficult platforming required. There will be 15+ endings based off of your decisions you make in game.

So tell us a little more about Harold  Where does he live? Is it a fantasy world or more like real life? What's his goal? What other characters are playing a role?

You have to define your world at least loosely otherwise you may end up with something that feels tacked-together. I could say here it would be fun to swing on a rope but perhaps that doesn't make any sense in your game.

Don't confuse this with elaborate storytelling, but just use it for yourself as a general guideline for things that happen in your game.
Hope this helps.

He's just a normal man, in a normal world. You'll get to decide things like who he marries, some of his friends, college or no college, things like that. The idea is that the levels are supposed to represent the difficulties of navigating everyday life, with any mistake potentially destroying your life(restarting the level)

Perhaps you could give the player a choice whether he wants to abide by the rules or take a more riskful path, e.g. getting a job or do some shady business. That could open up a lot of possibilities.

Thanks for the idea man! 

I think that's a really cool idea. I'm planning out what choices you make right now, and that looks great.