This preseason, I played a bit more often with challenger and master tier players and saw their border more often, which made me realise that the challenger border is the gold border with some extras. Same for the master border. Only that that is the silver border. So I thought that maybe a mixture of green and white and black and blue or so would look quite sick? I'm just thinking how you could make that different, because I think Challenger and Master tier is pretty hard to get to. So those players should get the feeling of beeing special. Well they get that a bit already of course, but if the borders remind to gold and silver...I dont know. Maybe you could try to design new ones for Season 9.
PS: I also think that they dont harmonate very well with the honor 5 badge and the lvl 7 for each champ.
Think about it like you want, this is my personal oppinion and I hope new designs are possible ^-^