It all started when...
Don Punchatz, the illustrator who created the DOOM logo and the famous front box cover art came over to id in mid-1993 with a male body model. Don brought a nice camera to take pictures. The model's job was to strike various poses for the marine who would be on the cover of the box.
This scene took place in the art room where Adrian and Kevin spent their days creating the STARTAN tech base texture set, clay modeling characters, digitizing them with the NeXTCube workstation, scanning hospital slides for bloody walls, and listening to the screams from the dentist's office next door.
The body model took his shirt off and started posing with our plasma gun toy. Don asked us for suggestions so I started telling him that the Marine was going to be attacked by an infinite amount of demons. It would be cool if he was on a hill and firing down into them. The model was holding the gun in various positions and none of them were interesting to me.
He did this for about 10 minutes and we just didn't see anything that we thought would look cool on the cover. I kept telling the model what to do but he couldn't see the scene in his mind.
Frustrated, I threw my shirt off and told him to give me the gun and get on the floor – grab my arm as one of the demons! Defeated, he deferred. I aimed the gun in a slightly different direction and told Don, "This is what I'm talking about!" Don took several pictures. I moved the gun some, the demon grabbed my leg, other arm, etc. At the end of it we all decided the arm-grabbing pose was going to be the best.
And that's the story of how the cover composition was created.
I am the Doomguy.
(at least on the cover)