This discussion may contain spoilers!
Well I finished the first episode and since it seems like we won't be getting the second for a while I'll post some of my thoughts regarding what I've seen so far.
First off I will say that it is unlikely that snow is dead forever for a few reasons:
* Fables are thrown into the witching well to 'make sure they stay dead' implying it's not a permanent state.
* Fables regularly use magic to imitate humans, I'm fairly sure a good enough fable could whip up a glamor that disguises something or someone else as something like... snow's head. Considering the second game is called smoke and mirrors...
* Too much time has been spent with a character like snow for her to simply be written off without seeing the act or having an opportunity to alter the results. Generally characters you met 5 minutes ago will die but characters you've known for a while will stick around or get a dramatic death.
* Despite faith being dead the mirror could still find here but noted that she was 'protected by powerful magics' which implies that she's not dead and possibly neither is snow.
I'd also like to mention that there is likely more than one element in play here. I doubt that all the 'bad guys' are aligned in their intentions and there could be a shadow war going on that Bigby has gotten himself stuck in. Possibly like a La Resistance movement going on to overthrow the current Fable town government or similar and they're being assassinated and split apart by the serial killer. Since the two people who seem to be dead are all disenfranchised individuals with not much left to lose. In fact if you go and catch the Woodsman instead in the preview you will hear Bigby ask the woodsman who else is involved "The girl with the coat". Implying that faith was involved in this somehow and either the two had a dispute and she got offed or she was merely 'disappeared' by a faked death.
Note: I've not read the book so I could be dead wrong.
Furthermore, in the preview we see Bigby in a more wolf-like form but I gotta express my disappointment in the lack of a canid muzzle, instead he looks like someone suffering from Hypertrichosis as seen in this picture:
Instead of something like this:
Which I honestly think looks scarier.
On a last note the first episode really reminds me of Iron Kissed from the Mercy Thompson series. Which (spoilers for those who've never read it) involved a Fae hating 'Mundane' getting a hold of several greater Fae artifacts like the Gauntlets of Giant Strength which is why the Fae that were found looked like they were decapitated by a werewolf or other massively strong creature rather than a bladed weapon like a sword or axe. Which is initially blamed on another Fae because the leaders wouldn't fathom a human killing a Fae. I doubt it's the same case here but it would certainly be possible considering that the Fables have a large stockpile of magical artifacts.
EDIT: It is worth noting that the achievements for the next episodes are visible, you can glean a little bit of information from it.
EDIT2: Now I played through a second time I noticed a few things. The 'Ginger Man' was the last person other than the main characters seen before the murder presumably occurred. When the head's found outside he's walking inwards right past where it would have been. His shirt has the same color and texture as the cloth (So does the guard's) and he was the cab driver for Snow White's Taxi the last time she was seen alive. Now this doesn't mean he's the killer but likely he's a lackey. Gren is first seen perfectly healthy trying to get help located a missing lady, later he's seen in the bar with a white eye, several scars, and an open wound on his shoulder. Implying a third victim and that Bigby isn't the only one getting screwed over.