I've been asked about the fellow in the previous post with the skull motif on his helmet. I'm far from an expert on Finnish WW2 uniformology, but this motif does appear in several photos from the period. Though to be honest, many of those may be Continuation War, not Winter War. As near as I can tell, it was used mainly by dragoons and light infantry, mostly in the Karelian area. If anyone out there knows more, please let us know!
Period photo, but it looks like non-winter uniform.
Reenactor, so take it for what it's worth, but definitely winter gear.