Well at this point I’m not sure of anything… I believe that now this is not only the box art that is the problem. I use the game cover, stream preview and communities images.
At the moment I do have a caching system… Could this cause problem? I fetch all the images from Twitch’ service dynamically but I “cache” them to make sure that I avoid recalling the service for the same images. If so, I surely can remove this system.
I will try to contact the legal team again since they did not answer the first time. I will try to put as much details as I can.
I really would like to publish it, I’ve worked hard on it. For sure, sadly, the only option that I see right now is to put only the text. Maybe it’s gonna be the temporarily solution.
Also, thank you for the links, it seems interesting to see how they handled the fair use!
Thanks for your answers! 
I will post the results when I will have some news.