Fury of the Furries had a quite nice use of cold-browns for rocks in its "ice levels". Same for "prehistorik 2" and "fire & ice".
reference pictures hereDonkey kong country levels in ice cavern could also be a good inspiration source. Iirc, a larger spectrum of cold colors (from magenta to cyan) was used. Maybe ground spikes could use that magenta shift.
Btw, you're really doing good progress on this. The whole stuff is über-cute and itches both my player's thumb and coder fingertips. I push my 2 cent into an edit.
throwing bonuses and monsters might bring more colors too.
I tried to 'smooth' the snow on the block just below your character. I have the feeling that your current snow is too much like white grass (and it could sure be done better than i did.
Gameplay-wise, i'd question snow on icecubes. Wouldn't it be better to have them "naked ice" that would be slippery (and visually distinguishable from snowy-rocks-that-you-can-easily-walk-on) ?