I mostly only notice the mouse urine smell, and it seems to be stronger with younger/smaller mice. If they were frozen immediately after being killed, that should really be the only source of stink--but as a dead animal, they will start to funkify after a few hours at room temp. And if you accidently cook them under a heat lamp and the snake "pops" them during constriction, then you'll REALLY get a nosefull...

Thawing them under dripping water like a frozen chicken breast is a good way to get rid of the worst of the smell--and it minimizes the time they have to go "off". But honestly, my snakes seem to prefer the icky mouse smell.