What if we found out that it was the man with the TTG shirt on in 400 day billboard? Or possibly someone who worked for Tell Tales?
There's pretty much no reason to think that. Most of us are just trying to rack our brains thinking who it could be, and picking the most outlandish things we can muster in the name of shock value.
Clementine does not know him. At all. They have been in the gas station, but Clementine didn't look at the billboard. Plus that would equal fourth wall breaking if that guy was made into an actual character as a former telltale employee. It's pretty nonsensical.