How do gory images lead to nausea?
The connection between eyes and food pipe had to do nothing with the motion sickness because the visual inputs and outputs to these sensory information are processed in the brain itself, So there is not need for eyes and food pipe to be connected together in order to cause nausea.


  Vasovagal response or vasovagal response or vasovagal attack (also called neurocardiogenic syncope) is a malaise mediated by the vagus nerve. When it leads to syncope or "fainting", it is called a vasovagal syncope, which is the most common type of fainting. 


(from http://en.wikipedia.org/wiki/Vasovagal_response)

This case is most commonly seen in adults and adolescents. There are several syndromes which comes under the vasovagal syncope which consists of symptoms like loss of consiusness,lightheadness,nausea,sweating,tinnitus,confusion,altered heart rate,fuzzy thoughts,cloud like spots in vision etc.


  Vasovagal syncope occurs in response to a trigger, with a corresponding malfunction in the parts of the nervous system that regulate heart rate and blood pressure. When heart rate slows, blood pressure drops, and the resulting lack of blood to the brain causes fainting and confusion.


(from http://en.wikipedia.org/wiki/Vasovagal_response)

Several pshychiatric disorders can cause vasovagal response like,



Agoraphobia
Obsessive–compulsive disorder
Social anxiety disorder
Blood-injury phobia
Hemophobia
Traumatophobia
Trypanophobia




http://www.nwocc.com/Pt%20Education/neuro_syncope.pdf http://en.wikipedia.org/wiki/Vasovagal_response


  When it comes to seeing red, the faint feelings could be tied to a phenomenon called blood-injury phobia. According to WebMD, this condition evolved as a way for humans to cope with threats:
  
  "The idea is that back in time, when someone was coming at someone else with a sharp stick or rock, a kind of genetic variation allowed certain people to faint in response," explains Tyler C. Ralston, PsyD, a clinical psychologist in Honolulu, who treats people with blood-injury phobias. Warriors who fainted looked dead and were passed over during battle. The blood pressure drop also might have helped those who were wounded avoid bleeding to death. Survivors then passed on the "fainting" gene.


(from: http://www.popsugar.com/fitness/Why-Sight-Blood-Makes-You-Feel-Faint-3061135)

"Overcoming Obstacles in CBT" written by Yvonne Tone and Michael McDonough states a condition about a patient having similar psychological problem described in the question. Here the patient's panic is associated with "gory images" of injury or illness, and his responses included intense nausea, pale skin, sweat and sometime fainting. He also reports avoiding gory scenes on TV/filim and medical programmes. The problem is identified as co-morbid panic/agoraphobia and blood injury phobia. 

http://books.google.co.in/books?id=1uIYqkKgKRYC&amp;pg=PA44&amp;dq=nausea+and+gory+images&amp;hl=en&amp;sa=X&amp;ei=qLZ2VJPMJ420uAS8qoHIBA&amp;ved=0CB0Q6AEwAA#v=onepage&amp;q=nausea%20and%20gory%20images&amp;f=false