Check this video out quick:
 (I hope that works! If not, it's, 'What Is Bill Cipher?' on Youtube)
There's one thing that doesn't seem to fit to me, and it's WHERE Bill came from. In the real life journal 3 (which I have, so I know), when Ford talks about his adventures in the multiverse, he says he visited the 2nd dimension, where he MISTAKENLY thought Bill was from. Now, this is perfectly plausible by itself, until you remember what Bill said in Weirdmageddon, 'Imagine living in the 2nd dimension...' I thought he wasn't from there! The video states that Bill is from the 4th dimension, and uses this as a reason to explain what his appearence and stuff like that. But they have proof that isn't very strong. I mean with the time stuff, 'cause the 4th dimension is a time dimension. But Bill only got the power to control time after he exploded Time Baby in Weirdmageddon, 'I control space, matter, and now that that dumb baby's out of the way, time itself!'. Sooo, Bill only got the power of time after taking it form Time Baby somehow! That pretty much rules out the 4th dimension, then,
So that begs the question: WHERE IS BILL FROM? This blog has just been me trying to gather any information, but if you have any more knowledge or anything, please comment and I will talk about it in another blog. Thanks!!