This was great! *very* rough around the edges, definitely needs a lot more polish, but I can absolutely see beautiful, shiny chunk of gold underneath. Ambience is great, graphics are great, the shotgun mechanics are fantastic, etc.
My main complaint is that the enemies are sort of boring. There are three types of enemy seen in this demo:
1. disembodied legs (see second pic). They walk towards you, dealing damage if they get too close, and take 2 shots from the shotgun to kill. Nothing special, but that's fine for a simple grunt enemy.
2. chargers (see third pic). A bit more interesting than the first enemy type, as they can charge at you, making them tougher to deal with. Their size causes them to get stuck occasionally which can be used to your advantage, but there really aren't any times in the demo where you can effectively take advantage of this. They take 3 shotgun shots to kill, and have pretty much no counters. Maybe they could have difficulty turning and stopping once they've started charging so you can dodge out of the way? I can see that combined with wider, more open spaces making for a much more interesting enemy type.
3. Big Boi (no pic). There's only one at the very end of the demo, which you encounter in a larger room with various pieces of furniture scattered about, as well as a lot of other enemies. Unfortunately, it seems to have the same AI as the first enemy type, sort of just running at you and dealing damage if it gets too close, made somewhat more intimidating by its larger health pool and increased speed. I can definitely see this guy working as a sort of mini boss enemy, though it could absolutely use some better AI, maybe some attacks that you have to watch out for other than just walking towards you.
A wider variety of weapons would also make the game much more interesting, especially if each weapon has its own strength and weaknesses. Maybe the shotgun could stun enemies and do a large amount of damage while having somewhat rare ammo and bad range? If you wanted to make it even more interesting you could give each weapon a unique effect, tailored to deal with certain enemies/situations.