Aren't you tired of asking everything crammed into capes? Sparkling vexillum was an original idea. They added fealty stars to clan cloaks. You also get a pet dragon. Jagex did good with the Tier 7 rewards. That should be enough. Sparkling effect to T7 clan cloaks would cheapen the max, completionist and true mastery capes. Honestly there is no need to add anything else. Although they could add some activity or mini game to give clans a reason to maintain those tiers.