Question: how to make custom login screen league of legends?
Answer: Head over to this folder: Riot Games\League of Legends\RADS\projects\lol_air_client\releases\0.0.1.94\deploy\mod\lgn\themes\loginBraum.
Change the name of login.swf to loginBAK.swf.
Take the custom login screen you want, and drag it in to the folder, and rename it to login.swf.