I've been with the idea of making your own concepts (regardless of how small the possibility that they'll be added to the game actually is) for a while now, and if you ask me, writing the lore, quotes, etc. is most of the fun of creating a champion. Naming their abilities, writing their quotes, making each part of them tell some sort of story, no matter how subtle or small; that is what gives me the most satisfaction in creating a champion.
Now, I've only posted three of my completed champion concepts to the Boards. That's not because I've only written three, it's because I've only really made three that I think deserve to be shared. That's not to say I think they're masterpieces, but relative to the amount of work and thought I put into them, if I can look at their kit, quotes, and lore and say to myself, "yeah, I don't regret a single second working on this champion," then I think it's worth sharing.
You've posted a lot more than three concepts. I browse the Boards a fair amount during my free time, and it seems like you've got a new concept every few hours. That's not to say you put less effort into them than me or anyone, it's to say that you've clearly got the creativity and are constantly testing yourself (hell, just yesterday there was a post for a "mechanically difficult tank," and within hours you had a concept up). I think you would do well to expand that creativity into the heart and soul of your champions. Who are they? Why are they here? What are their motives, their relationships with other champions we're familiar with? What story do they tell? Look no further at the importance of this than the way Riot has been handling their champions and lore lately. Gangplank's rework had an entire Bilgewater-themed event with it. Tahm Kench, Ekko, Bard, Braum, Yasuo: all of them had cinematics, web pages, games, animations associated with them. They all told a story.
So, my suggestion? Write lore for all of them. It doesn't have to be some hulking wall of text that's ten pages long, but if you get their background, interactions, and personality down, I find it helps a lot with creating a kit that not only flows cohesively, but just fits nicely with the champion as a whole.
As an example, I'm writing a concept up for Senna (Lucian's wife/love). There's a lot of questions to ask regarding how her kit should work: should it be like Lucian's, or was she her own woman with her own techniques? Well, that's dependent on her background. What should her kit's theme be: another purifier, one whose heart wasn't turned cold by loss, unlike Lucian? Could she give us a clue into what a purifier really is? Well, that's dependent on how her lore pans out; how did she escape the Lantern, what were the side-effects, did she become something more, etc.
Do you see how, in these questions, the answers lie in the lore? They lie in the champion's very nature?
That's what you should strive for. If you can imagine a champion's lore, background, personality, quotes, etc. clearly enough in your head that the kit is merely an afterthought, then you've got it made. A champion's kit is decided by their theme, and who they are decides the theme.
