Snow Wraith Island is a location that appears on Hiccup's Map.
This island was shown to have some small hills and a large lake in its center on the Race to The Edge Map. The island appears to lack any foliage and it sports a cold ice blue color, which indicates that its climate is rather cold.
However, on Hiccup's How To Train Your Dragon 2 Map, this island was shown to have several large spruce trees growing on it, which would mean it is warm enough for trees to live on.
Snow Wraith Island (also known as Glacier Island) appeared on this online map of the Barbaric Archipelago. However, no additional details were given about it on the map, nor did it appear in the Dragons: Race to the Edge series.