Magic the Gathering Finn's Aerial Maneuver

A few people had been asking me to try to customize Magic cards. Now, Magic is a game I know ZERO about other than some of the cards have cool art. But I saw some other artists attempting this and they looked awesome so I decided to do the same. I'm pretty sure this makes them "illegal" for tournament play. I don't know what I just said means, I just am repeating what I heard.