The overall composition is great in all the pieces, the only thing I would comment on is diversity of the theme. When one thinks of winter rusty leaves (browns & greens), and snow / snowflakes come to mind (blues / whites). Some elements of snowflakes building a face would have been exquisite. A snowflake or "snow element" encasing one of the faces.
Other than that I feel the colors fit the the theme you were going for very well. I also don't know if any lore or mythology is playing apart of the design decisions you made. Only three of the four pieces give me a winter vibe. The two up top and bottom right proclaim your theme to me. The last one seems a bit more morbid.
There is a definite spiritual sort of haunting beauty to them, and another thing they remind me of is like a Victorian elegance, with a touch of Davinci they are breathtaking, I'm turning to mush here because of them, thank you, Mike.
I love the second one (the red one) Is like impressive, I don't know how to explain. Did you paint it with blueberry tea? Cause I have it and it has the same color, but i didn't imagine that if you paint it would have the same color on the paper