Thank you all for your help.
Hiring a concept artist seems like the easiest, however I have no means to do so, I wish to make a game all by myself (CG and programming skills more or less provided) and last but not least, most stories I have seen are very far from being original, even if they came from a team of concept artists 
I was curious about the way of coming up with something new, if there are some footsteps to follow, a pipeline like we model props or build a program.
To Panicintrinsica: that’s what I thought, there are so many games that a truely original concept that has nothing to do with any genres is highly unlikely to come by I might just toss around ideas and modify them.
This kind of stuff comes easy when I model or program, but I’m not a great hit when it comes to the concept just yet 