Lets now speculate on who can be Gormogon.
As we've seen it in earlier episodes they've caught Gormogon 3, which then suicided, and gormogon 1 is about 80 years of age, toothless, and has Alzheimer's. However the second recruit is still out there and is pissed off that Booth and Brennan have discovered is secret lair with his pieces of art.
In more recent episodes we have seen the second gormogon try to kill booth and brenan and eventually succeed at killing his corrupter. If you watch closely that episode (knight on the grid) at the very end you can see gormogon's face... maybe not clearly but at least its something. And don't get me wrong, but i really think Gormogon must be considered as a male character from that last scene. We have to recognize that he is very athletic and smart to be able to escape Booth's attempt to catch him in the corrupter's house. Conclusion, take out Booth, all the female characters, Zack, Hodg out of the possibilities of being the killer.
One guy we might have considered, if only he wasn't in jail, is Brennan's brother. He's got all the attributes pointing at him. Dad was an escape artist, probably did some time in the system, became pretty smart working a bit with his sister and father, and he looks much like the last scene when we can see Gormy kill the corrupter.
Hope this helps confuse you all a bit more. :P