Well, no one seems to be answering this so...
I've never seen a symbol for snow or ice.
People normally use a shade of white, usually with a light texture on it.
You can find examples in the Finished Maps forum, but it will take some patience.
I'm currently making a map that contains snowy terrain (as well as many others), and I'm very not comfortable working with colors yet as I'm very new to even just drawing. Is there a way to draw/indicate a snowy region? A particular 'symbol' I suppose, like trees for a forest, tufts of grass for grasslands, etc.? If not, then that's fine and I can leave it be until I do get into coloring/shading, but I was just curious what other people might have thought up!
Well, no one seems to be answering this so...
I've never seen a symbol for snow or ice.
People normally use a shade of white, usually with a light texture on it.
You can find examples in the Finished Maps forum, but it will take some patience.
You could use snowflakes, if you want an iconic symbol. Without knowing what the map that is supposed to include the snow is going to look like, it isn't really possible to give specific advice. Most types of maps wouldn't include snow, a temporary feature, though they might include glaciers. In some cases, just a label with the word "snow" would be suitable. If you could post a work in progress (WIP) thread and show the map you are working on, you would likely receive more responses, and they could address the needs of that particular map.
As other said, it depend on the kind of map you are doing.
Most people would just have the land become white.
You could have pine trees and mountains covered in snow but please don't put snow in deciduous trees with their leaves still on. It might be easier to do, but it does not make sense.
For the texture overland, you could add a texture like this https://www.google.ca/search?q=snow+...w=1920&bih=966
My Deviantart: https://vincent--l.deviantart.com/
I'm definitely no expert, but for me I think it's more about the color scheme than symbols (although if your map is black and white, you might want to use the snowflake symbol as @rdanhenry suggested).
I'm posting a few links to maybe give you some inspiration. None of these are my works, I just googled "fantasy map elements snow" and browsed through the images. Post your map and everyone might be able to provide better insight. You may just even texture the area with dots or cross hatch or something similar that is unique to only your snow areas and simply label it such in your key. Hope this helps.
https://vignette.wikia.nocookie.net/...20080913162004
https://i.pinimg.com/236x/83/02/b4/8...gs-rpg-map.jpg
https://pre00.deviantart.net/27be/th...ef-d7ft5bz.jpg
http://moziru.com/images/drawn-mountain-map-5.jpg
~ whisper