None of this is canon, and it is only fans' takes on the events due to the lack of canonical explanation.
- Since the Impaled heads are likely part of a plan by Vigo to dissuade the Ghostbusters from exploring further into the subway, it is possible that the heads are representations of Vigo's Carpathian servants/victims.
- Another theory is that the heads actually belonged to the people who died in the City of Albany Accident, when the old New York Central accidentally derailed and killed over 100 people and the Disembodied voice belonged to one of the dead victims if not the first head to appear in front of the three Ghostbusters. This would explain why the Disembodied voice, Impaled heads, and the Ghost Train all showed up in the same time.
Behind the Scenes
The crew made a call all over New York for 'dead heads' and took whatever they could find. Pam Easley, visual effects coordinator, made the calls. Rick Lazzarini made a few. The better detailed heads were placed in the foreground and the lesser detailed ones in the background. 
- One head in the left foreground in close ups was sculpted by Adam Jones, who later became a guitarist for Tool.
- On Cover A of Ghostbusters Issue #16, the Impaled Heads appear in an homage to the Ghostbusters II scene.
- Among the effects artists who worked on the heads was Adam Jones, who would later become the lead guitarist for the rock band Tool.
- Eisenberg, Adam (November 1989). Ghostbusters Revisited, Cinefex magazine #40, page 26. Cinefex, USA.
- Wallace, Daniel (2015). Ghostbusters The Ultimate Visual History, p. 177. Insight Editions, San Rafael CA USA, ISBN 9781608875108. Rick Lazzarini says: "There's one in the left foreground in close-ups that we created and supplied. It was sculpted by Adam Jones, who ended up being the guitarist for Tool."
- The Character Shop: "A decapitated, mummified head, featured in a great, big close-up in GHOSTBUSTERS II. Sculpted at TCS by Adam Jones, now guitarist (and music video director for the band "TOOL"."