LoL Custom Map Skins - Are the skins allowed or not?

Greetings This type of a thread has probably already been opened somewhere, but google and the inbuilt search engine on the forums weren't very helpful. So since I've been thinking about using some, just to spice up the rift, I've wanted to ask what the official opinion on this is. Are they allowed or not? The guidelines on Riots page is that everything that changes the game from the point you click Play until the end-screen is prohibited and against ToS. Since this practically does change the visuals in game, I am not quite sure and would like an answer from someone that has official knowledge on this. I don't want to put my account in jeopardy just for a visual change. Thank you
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