First impressions:
#1. This image does nothing for me - I don't see anything to tell me that it is winter. You did say that you were
going for the cool winter effect.
#2. This isn't bad, but I would have tried (maybe) to have the tree's shadow in focus as well. As it stands, only the tree trunk is in focus. You might think about shooting these types of images in portrait mode. This would show more of the tree and its shadow and get rid of some of the OOF background on the left side of the image.
#3. Personally, I like this one - nice silhouette. I also like the clouds in the upper right - they tend to break up the monotonous blue sky. ( Alberta has some very blue monotonous skies - I know from shooting scenics all over the southern prairie...this is why it is nice to have the monotony broken by clouds every once in a while.)
#4 I really love this one. The placement of the orange-brown scenery against the very dark clouds - very nice capture. The two trees on the left following rule of thirds placement and the horizon is in the lower part as well. The only thing I would do is crop out the shadow area in the bottom of the picture. For me, it is a distraction. I know your part of the world very well - would you care to tell me where this was taken - looks like a golf course somewhere in the city.
#5. This is a nice snapshot, but if you hadn't told me what it was, I probably would not have known. It is not obvious to me, at least, that the upper 80%± of the image is ice.
#6. I am not sure about this one - does nothing for me, but if you like it, then that is what counts. Might have been better to have the foreground in focus as well, but that is just me.
You say you are working on composition and exposure.
I would encourage you to surf the web, but you could start with - Advanced Composition -- Part I - there are two following web sites with the links at the end of the site. As well, have a look at this one - PhotographyComposition Articles Library as there are a number of links to sites on composition. There are a number of books that have been written on composition - you might want to look at one by Bryan Peterson called Learning to See Creatively - Amazon.com: Learning to See Creatively: Design, Color& Composition in Photography (Updated Edition) (9780817441814): BryanPeterson: Books. There are lots of others.
As far as exposure is concerned, Bryan Peterson has one that he wrote on that subject as well -
Understanding Exposure, 3rd Edition. I would recommend this as an introduction to the subject. You can also find a lot on this on the web - Google "exposure triangle". HTH.
Cheers,
WesternGuy