I have attempted at least making a map with theme (all pines trees) but I fail at even that. So, if anyone would like to take up the task, I'll leave some suggestions for a winter themed mod, maybe in Alaska or something:
Realistic woodcutting:
While you can cut down any old tree for building
structures, you need dry wood for fires. Perhaps
implement some type of woodshed in which you can
store wood and after a week in game time or something it becomes usable firewood.
Farming:
It'd be pretty hard to farm, so there'd have to be some pretty major changes. Perhaps replace it with a foraging skill, in which a player can search shrubbery, identify, and collect wild edibles (i.e. forage in a bush. certain % chances to find edible plant matter, berries, etc, rather than just having berry bushes).
Fishing:
Ice Fishing! I dunno just revise it you you can catch actual realistic northern type fish like trout, salmon, muskellenge, etc, with each satiating your hunger or healing your health based on average size. This of course depends on where the mod is based in real life, if anywhere in particular at all.
Hunting:
Introduce snaring. It's hard to hunt big game without high powered rifles, and implementing snares and other traps would allow you to catch rabbits and birds, which is more realistic if you're stranded in a barren tundra or something like that.
Shelter:
Try introducing a few new shelters, like a snow shelter (dig under a deep snow pack, almost like a makeshift igloo with snow rather than actual ice blocks). An igloo too could work I suppose, and tree shelters (in say, 6 ft of snow, you dig down to the ground around the base of the tree, live down up against the tree trunk, and pull the tree branches over the hole). I imagine the latter might be hard to make but its an idea.
Also, introduce another needs type meter regarding body warmth. This would drop at different rates each day, simulating some days being colder than others. To "heal" this stat, you'd need to spend time in your shelter or by a fire. If possible as well, work it in with the fatigue meter. They say not to work yourself into a sweat in a cold wilderness because your body temperature will begin dropping and that, combined with the cold, will quickly lead to hypothermia. Thus, is possible, make it so that if your fatigue meter gets too high (presumably from overworking), your Body Temperature bar will start to drop faster, thus emulating the point I just made.
Just some suggestions for a mod that I think some people would really appreciate for a change of scenery. I like woodland and arctic survival better than tropical on shows and stuff