I applied the CoterieCraft resource pack in a world where I had multiple peoples' heads. The resource pack was for 1.7, and I immediately noticed that my own head had become that strange amalgamation of Steve that happens when applying a 1.7 skin to a 1.8 skin size. I immediately deactivated the resource pack, and my head stayed Steve. I deleted all of my SadGhoster87 heads, and gave myself a new one. Still Steve. Reloading, relogging, logging off and back on, nothing worked. The other people's heads stayed as their own, but my head stayed Steve.
Steps to recreate:
Apply a 1.7 resource pack in a 1.8 snapshot world containing player heads.