skin preview ?

They claim: The program is not breaking any terms of service, so its all legal/legit to use and Riot won’t ban you

If the program offer only some texure change ( use of skins ) on our pc you won't incur in ban... may result in a ban the use of any program that offer in-game advance of any source

Sooo use it at your own risk but if it's only for the skin they can't ban you