Dynamic backround bug

Ok so, this is my first time writing a discussion so bare with me :D. I main Karthus and have 11 out of 20 games played (recently) however i had 8 games with katarina but my profile backround shows katarina... This really bothers me as i hate the katarina background....I also have the Grim Reaper skin for Karthus- im not sure if it will show up but i would really like it if would atleast show the normal Karthus backround. I have most worshippers on Karthus and more recent games on Karthus... But is showing katarina who i have no iterest in? Please help if anyone knows any more info! Thanks for reading :DD.