this has been happening to me for months - whenever i log on to my blood elf paladin, for some reason, he’s got the model of a manafiend over him. the link is the specific type of model that’s over him.
i’ve tried just about everything to try to fix it myself - reinstalling, repairing my install, taking off all his gear, putting everything he owns in the bank, randomizing his appearance in the barber shop, changing his spec - the list goes on and on.
i do not think it is something with my install or my addons, as this persists on different devices as well; i logged on to my partner’s computer and the manafiend was still over my guy. other characters cannot see the model over me, it’s just on my side regardless of device. as far as addons go, i have very few and it still persists if i have every single one turned off or uninstalled.
i’ve tried sending in support tickets but they’ve been pretty unhelpful so far, so i’m hoping someone on the forums has an idea on how to fix this 
it’s made my guy unplayable which makes me very sad.
Oh! I remember this!!
There’s a Dalaran quest where you have to test a manafiend experiment. Long story short, if it glitches, the only way to get it off that I’ve ever seen is to queue up for an arena match and then leave. Give it a shot, see if it works?
i’m absolutely shocked, but it did work! thank you so much, this has been bothering me for months 
You’re welcome - I’m just glad it still worked! 