I can assure you rioters are constantly lurking on these forums, but they don't post because they're scouting for originality and creativity. In the same way a university sports scouter doesn't tell you how to stand out, they would stay in the background until you stood out by yourself.
Pool party ziggs, pool party Leona, battle bunny riven, pop star ahri, medieval twitch, void fizz are all skins that were inspired by player concepts. I know pantheon ultimate design was also inspired by a player, but I'm not sure about other abilities. I'd also like to think that parts of the sion rework were inspired by a post I made on the old forums. Even ability names are named after certain contest winners.
The point is that you have to keep posting and refining your skills as an artist. When you hit a home run, you can rest assured a rioter will see it. It might take months or even a year, but if you have something really good, it will show up in the game even if it's a subtle addition.