This is a tool that produces a custom League of Legends Champion Select Overlay that is inspired by the one used in the LEC and LCS between 2015-2017.
Just download the latest release for your platform and you are nearly ready to go.
After downloading you have to press the button Update Champion Images.
After that you just have to join a custom Lobby and press the button Start Overlay.
If you want to fetch the summoner names of the players in the Lobby just press the button Fetch Summoner Names.
If you want to build your own Overlay, there is a module that exposes an API for easier usage.
The module can be found here