Minecraft forums probably, or any of the forums run by the major launchers (Feed the Beast, Technic, maybe Curse though I don't know if they have forums, not sure if others exist). Reddits for general minecraft modding or those launchers.
You're not going to be well-received, though. A lot of people have ideas they'd like to see happen (not just in minecraft but in any creative endeavor - games, writing, movies, music, etc), but feel they lack the technical expertise necessary to realize their vision. The people who do have that skill have their own ideas they want to see happen, and those are going to take priority. If they have the skill but not the interest (in the idea specifically or in the setting), then it becomes simply work... and most likely unpaid work at that. The best you can hope for (and this is itself unlikely in the extreme) is that someone will take a fervent interest in your idea, but that just means they're going to interpret it their way. You won't have any more control than simply an 'inspired by' credit, if that, and it won't turn out the way you'd like to see.
The alternative is to learn to mod yourself. It can be daunting to start, depending on how familiar you are with code grammar in general, but it is the best option. Just don't jump into the deep end to begin with, start simple. Change a vanilla block's name. Copy the block. Change its recipe. Change its texture. Do the same for a tool. Same for entities. Now change behavior: make a hoe act like a pickaxe. Make a furnace act like a hopper. Make cows shearable (either for wool, or change it to be leather). If you don't know how to do something, easiest way is to look at a mod's code that does do that behavior - an example would be how Witchery causes villagers to seek shelter at night and sleep; however, some of these are likely depending on the Forge API.
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Topic: Minecraft - It has blocks. (Read 2457619 times)