How to define custom shape for snow effect?

Hey guys! I want to make a Christmas card for my friends but i’m lost. I want to add snowfall in this picture, in the globe to be more specific.

I’ve looked up all night for scripts and some tutorials to help me out; i’ve searched the forum too and i didn’t find nothing that i could use.

Now i barely can keep my eyes open and i must finish this tomorrow. I hope someone can help me, i’ll really appreciate it. Thx in advance :thumb2:

PS. i hope that what i’ve wrote makes any sense :smiley: ZZZzzzz :sleep: