I see you opened the applications already, but as a cosplayer, I remember 2 years ago we could put our pictures of our cosplays on the application, now I don't know how it should be... Do we just need to write down what we have? Or should we add links with the pictures?

Hello, there ia a place for this in your profile - portfolio. If you choose edit profile option, go at the bottom and you will see a place to add your photo.
Application will be seen together with a profile for the judges.