The content you posted was not only not made by you, it was literally screenshots of GTA V. It was barely modified, and it's something anybody can do if they have the game. It's not much different to making a 3dcg thread for your minecraft builds.
if you look at the other posts on /3dcg/, it is either user generated content or content that is 3d and guro. GTA V is not guro, nor were these screenshots even modded to be nude, it's just dead ragdolls.
I don't mean to dissuade you, but please try to have some standards in what you post.
That's fair, but it should be enumerated in the rules that threads should contain content created by OP.
Are you aware of anywhere else that shares this kind of content?
To be honest, Steam would work great. Your posts would not violate their ToC.
Youtube probably? I know that there are a couple channels that specialize in ryona videos for videogames.