I cleaned up my hard drive and found this picture.
The file is dated 1997, so the source must be older (obviously). It is probably related to the computer game Doom by id-Software. Somehow, that was the first thing that came to my mind after i saw the image for the first time after 16 years ;)
The monster looks similar to the Doom Cyberdemon, thats all i managed to figure out.
I don't have much hope that someone comes up with something, but i thought its at least worth a try. It may even be fan-made, but somehow the monster looks too "good" for that.
After looking at the picture again, I noticed something familiar about the background. Look at the picture below. Those are textures from the Doom game. Doesn't the third one look like the background? While this does not explain where the marine/monster comes from, it supports the fact that the picture really is Doom related and that it probably has been edited. Or maybe I am seeing things that aren't there ;)