Custom HUD

I remember using a custom HUD a few years ago and it was actually quite nice because of the way somebody could customize the game without influencing the game (like skins!). Now, after 2 or 3 years I have noticed nobody talks about these custom HUDs and so I am wondering if there is something wrong with them (like not adhering to Riot's rules?) or if they are just not well known. I'd really appreciate it if somebody could tell me if it is OK to use them and where I could find a few of them.