If you want to be completely locked to the theme, go ahead and build it like this, but know you're intentionally building a sub-optimal version of the deck because of it
Mostly this is good in this deck in the same way it is good generally and that is for the midgame mana boost and the late game value generation without having a significant early game cost
Creature spells you cast cost less to cast for each creature you control with a +1/+1 counter on it
Atraxa, Praetors' Voice allows you to proliferate each turn to scale up the abilities of any cards with counters on them
Helm of the Host is the most recognizable combo here, which works with a number of other extra combat cards too
Most of your frosty forces will be overlooked while the -X/-X effect, which gets around Indestructible, Regeneration, and Protection abilities, whittles away at enemy armies