Génération d'images générative d'univers de fiction : Harry Potter, Stranger Things etc

You need to know that those items are highly merchandised and to be able to use anything like this commercially, you will need to pay license fees. If you do your own costume for your own private pleasure, that will be something different from using your work in a public place. 

There is no way to do a costume that comes near to what your favorite character wears and not violate the copyright on that design. So in all cases, you would need the authorization of the copyright holder.

This is also true for your private corner. You are violating the copyright if you copy something, there just won't be consequences for this. 

Your best chances are to join a fan club and to see what they do offer on this topic.

(This is no legal advice on copyright. I'm not an Adobe employee. I doubt that Adobe employees will say more into this than what @CMass said.)