Lots of fun & experimentation with blending modes. Ultimately settled on my usual blending modes.
Added colour fill over watercolour overlay & set blending to screen, 100% opacity.
Clipped photos to framed masks, clipped colour fill to photo & set blending to overlay, 67% opacity.
Set blending mode on large snowflake element to Colour Burn, 70% opacity.
Added another edge overlay. Blending set at normal, 100% opacity but added a white colour fill.