Experienced Architect with a demonstrated history of working in the graphic design industry,Strong arts and design professional with a Master's degree in Sustainable Architecture
Based on my experience in winter mountains rather than 3D knowledge, If you're aiming to photorealism:
- The snow on mountains has drifting patterns. It's blown by wind and the different layers slide over each other. The fact that the water has some waves suggests there's some wind. So you should add some random displacement to the overall snow.
- The snow closer to the water should be patchy, because the water is at a higher temperature than the snow above it and usually it "bites" chunks of snow
- Steady snow has a thin crust of ice on top of it which is reflective. It's not as rough as it's shown on your render
- Lighting is great, you nailed it
- The snow accumulates based not only on height but also on the aspect of the slope and where it's facing. Slopes with a low angle would accumulate snow as much as low lying terrain. E.g. the small hill to the right should be covered more in snow as it's not as exposed to the sun as the other and also has an easy angle, not too steep for the snow to fall down.
- From the color of the light, it seems like early morning, so given the sun hasn't been up for long, there should be some fog over the lake and to the right

Hope it helps!