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So far I've only noticed this in practice games. I'm pretty sure it'd be obvious if it appeared in normal games. In case it isn't clear, its the little "broken graphic" icon in the dead center of the screenshots.
Edit: Confirmed it appears in normal games too, it draws just underneath the 5th summoner's second item.
2009 iMac 27"
2.8GHz Intel Core i7
ATI Radeon HD 4850 512MB
2560x1440, all settings Medium, no shadow.