Hi. When you go to Settings > Data usage > and tap on 'Media', you will see a list of what your Media is made of. Typical apps that makes up 'Media' are 'Media Storage', 'Download Manager' and 'Downloads'. If you are rooted, you can use Link2SD to freeze 'Media Storage' which carries the greater part of system-based storages which may require network connectivity. You may have issues with screenshot and the likes afterwards though.