custom traps?

How can I create custom traps like freezing and damage over time trap?

Freezing would be kind of similar to stasis, just with different artwork, no?

Other than that, trigger it.

I dunno how to make a make the trap give the art and buff when it goes off or even how to make the trap go off when a unit gets too close.

Make a dummy caster to cast Ensnare (or something like it) when a unit gets to close to your trap. You can change the model to an ice block if you want. Make a trigger that detects when a unit comes to close.

How come a Statis Trap fire and give the buff without triggers?

Its hardcoded... you can make trigger that makes stasis traps every 15 seconds (too less can result in perma-stun).