It looks like the decision on the colors has already been made but I will add my analysis as well for the record.

The first image, with the charcoal looking background lends itself to the idea of darkness and it highlights the water such that it seems significant.
The second image lends itself to icy-cold and the river is not as significant because the entire area is trouble (this is because the whole area is shrouded in ice or at the very least cold).

So if the second is what you want it sounds like you choose correctly.