The game looks like it needs a lot more work. You seem to be using placeholder art in your screenshots, that may discourage people from supporting your campaign. The theme is not original at all, zombies were a huge thing back in 2008, now it is just boring and repetitive.
The top down shooter market is very saturated, you'll have to radically differentiate your game from the crowd for any hope of success.
That's just my two cents, good luck!