Custom Skins!?

I do believe you will be banned. The program for bans can be automated, and I do believe they will consider a custom skin to be a third-party addition to the game. Which is not allowed, and a bannable offense.

You'll be banned eventually; There were a whole bunch of people way back in 2014 - Thousands if I remember who all got caught up in a ban wave for using custom skins. All had there accounts permanently banned; no questions asked.

Your account: ********* was banned due to the use of malicious 3rd party programs or modifications to your League of Legends client. We believe that all players should play on equal footing in an effort to promote competitive sportsmanship. You should be aware that modifying your League of Legends client is against the Terms of Use: http://na.leagueoflegends.com/en/legal/termsofuse. We hope you can see that it is unsatisfying to play against other players who are using a tool to gain an advantage over others.