dynamic background bug

i dont understand your dynamic background thing,

out of NOWHERE lee sin pops up as my background, and i haven't played him in like past 200

can you like fix that so it ACTUALLY MATCHES CHAMPION that you played THE MOST in PAST 20 GAMES?

this isn't even the first time random champion shows on my background, or sometimes i play 1 game with champion , yet 19 with other one , and this 1 gets to be visible.. like cmon riot