I don't know if this is loaded automatically by Twitch or something. But the icon is outdated, maybe peppy you'd like to change it since it looks just like that old osu! background, just a detail you may like to change.
twitch uses the Giantbomb API for their games list, so you'd have to contact them in order to change the icon (and maybe even remove the capitalization from the "o", though I'm not entirely sure if that would work with how Giantbomb lists things)
I am in contact with twitch already regarding this, and was even told my new art would be used, but it hasn't been updated yet. If anyone has a reliable twitch contact please contact me.