These are the ice textures that i use most commonly and find to be most effective.
In my experience using the snow overlay texture over the blue ice texture creates a very effective frosting appearance which i used in my map Snowthistle for this frozen waterfall.
You're going to have to be more specific than that. light_env sets the color, intensity, angle, and diffusion of shadows. In other words, it controls the light you actually see. The skybox is merely a set of materials to match the lighting you choose.
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