for the snow effects.
either you use for example the sand effects and just tweak them (not sure if they will overwrite the original sand effects.
or
you have to create 'new' effects, materials (so the game knows when to play snow effect X etc), sounds etc and than mout all that in the map folder (objects_client, objects_server, common_client, common_server)
so quite a lot of work, but to speed things up you could 'just' tweak the current sand effects (replace yellow/brown with white/grey, add some more dirt etc) rather than create totaly new ones (there are a lot of different effects that would need to be done). also the material thing shouldnt be overlooked as well, as its quite a mess to do






