First of all, it's important to remember that this is an account drawn from an true event that occurred when Orwell worked as a British colonial official in Burma. It is a nonfiction story that some critics call an essay rather than a short story. Having said this, we may suppose that Orwell actually did encounter a Dravidian Indian killed by the violence of the elephant and that he was in the position of or similar to the one the narrator of "Shooting an Elephant" describes.
Therefore, while Orwell may choose the language to capitalize upon the sight and event and while he may incorporate a writer's perception of symbolism, metaphor and irony, we cannot assume symbolic significance in Orwell's descriptions. Having said this, if this were a fictional story, the crucifix would allude to the Roman crucifixions on Calvary Hill, the most famous of which are the crucifixions of Jesus Christ and the thieves who were crucified near to him.
Therefore if the man's position is looked at as symbolism it might be seen one of two ways. It might first be seen as the sacrificial offering the elephant required to quell his wrath since afterward, he is found as peaceful as a cow:
the elephant was in the paddy fields below, only a few hundred yards away. ... at that distance, peacefully eating, the elephant looked no more dangerous than a cow.
On the other hand, the man's position might symbolically represent the injustices of an oppressor conqueror since Jerusalem was occupied by Roman imperialists at the time of Jesus Christ's crucifixion. The language Orwell chooses to represent the event may therefore be understood as part of his complaint against colonialism.