I created an account only for this comment
If you're truly 

Adrianks74

I'm ecstatic you're continuing your old project. Do what you think is best and continue adding content, I greatly fondly remember playing it back in the day with friends. I know you'll do good, even how the original ZumbiBlocks was left there was more than enough to mess around with for a long time.

Ignore people comparing visual styles(unless you truly want to try something new) they don't know and will always compare to something.

The only thing I could recommend is multi story buildings to the map, or buildings similar to what was in the original(IE diversity, destroyed buildings, planks connecting ground to roofs and roof to roof, etc.)
Possibly a boat you can collect components for so you can go out on the water for safety or a safe house/room, IE the swarm nights/zombies that know where you are even when hidden away
And if it would be possible when selecting a difficulty, it stays that way OR when you kill too many zombies too quickly it will start to climb up. But if you chill out and don't kill a bunch it'll climb back down. Like police wanted levels in videogames. The way it is now makes it difficult to wander, collect, and explore.

Unless the game design you're going for is a push to see how long you can last type then disregard my pointers, maybe something to think about for another gamemode maybe?

Either way I hope you are doing good and well for yourself and am glad you are able to pick up the passion project again, I'll keep my eyes on this page and hope for the day it hits steam so I can support you :)

P.S. Why did you remove Zumbi Blocks off of kongregate?