Sorry, Lily, only just noticed this thread!!
I've asked Kitts if she can remember which ep you're looking for (if it's from the original VS) as, firstly, she put all the pictures in, and, secondly, I've never seen House of Wax so wouldn't know a still from that film if it bit me!
If you had the baddie's name it might help me find it if Kitts can't!! (I thought it might be Stasis or Laura at first, but I can't see any pics like that in those eps!) I honestly don't remember anyone getting their mouth glued shut, although it sounds like something Tree or Terry might have written!
Oh hold on, think I've found it! Try Devil Game by GaelicSpirit:http://www.supernaturalville.com/s2/devilgame/devilgame1.htm