Are there any more poetic synonyms for "snow-white" and "niveous"? I was searching but I've only found "nival".
Comparisons or contrasts like milk-white are sometimes used; eg, in Surrey with the Fringe on Top,
[Shirley] Has it really got a team of snow-white horses?
[Gordon] One's like snow~the other's more like milk.
and in Lamentations 4:7,
Her consecrated ones were brighter than snow, whiter than milk...