Sorry to hear that your original project got deleted somehow during the jam! That must have been one hell of a hurdle to get over, and I think it's fair to say most people would have given up at that point so hats off for you getting something in on time!
My thoughts are similar to many of the mentions below; increased variety, sound of the gun, sound of the zombies (as it's pretty terrifying to turn around to a zombie you have no idea is there haha) and some kind of more linear progression would certainly add a lot. :)
That said, shooting things in VR is always pretty satisfying isn't it.