Iron - Haven't been there, and I don't want to judge without actually knowing them.
Bronze - The stereotypical "I'm only here because my team always sucks, they're uncarriable afk inters." Although that was mostly in Season 4, since that this may have moved into Iron, I'm not entirely sure.
Silver - The all knowing elo, aka "I have all the game knowledge, I know everything about the game, and Riot should balance things differently, change the matchmaking, etc..."
Gold - Honestly I think it may be one of the chillest elos, at least that's where I had my best time playing League.
Platinum - A literal zoo, where people are Gods, and if you're not plat or better, they consider you to be a waste of oxygen and all your arguments become invalid. I legit had games in my plat promos where we had a Gold 2 midlaner, and a Plat 3 jungler, the jungler kept complaining from the very start "gg ff at 15, we have gold players in the team", and the midlaner was doing fine, the jungler sucked, but the jungler kept flaming the midlaner and said that it doesn't matter that he seems to be doing great, nothing he says has any validity because he's gold. And these kind of games happened very often. The most toxic elo I've seen.
Diamond - Similiar to plat, but not as bad. Diamond players however seem to play tons of ARAMs because they're hardstuck and can't win rankeds, and whenever someone's flaming the shit out of their team in ARAM, it's a diamond player most of the times who takes ARAM deadly seriously even though it's just a fun gamemode. Majority of them also seems to be really bad at the game.
Master - On SR (normals) they seemed to play quite decently and were less toxic than other elos, however still didn't play as well as I would've expected. On ARAMs however they are always so horrible and feed.
Grandmaster - I don't remember ever playing with Grandmasters, I probably have but I just can't remember.
Challenger - Well, the only way I matched up with Challengers is on ARAM, because I don't think they really play normal SR, they would just play ranked instead. But anyway, so far the ones I've seen were very decent, legit 1v9-ing the game sometimes and the team mostly plays around them from the moment their border shows up on the loading screen.
Which points do you agree/disagree with? I based everything I said on my personal experience, so I don't want to claim them as being "facts", these are only my honest opinions about each elo.