If you want smaller flakes, lighter snow here's a few I created that might work for you.  Copy the code into the CSS Box leaving a whitespace between codes and Save. It should be the last code.

Merry Christmas
RMMusic, Larry

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Light Snow 1

#main_body{background:url(https://img1.dreamies.de/img/85/b/fdx4d9tkg9f.gif) repeat fixed top right; }

Medium Snow 1

#main_body{background:url(https://img1.dreamies.de/img/434/b/nt0k467hpmq.gif) repeat fixed top right; }

Medium Snow 2

#main_body{background:url(https://img1.dreamies.de/img/878/b/tocc0uslxfa.gif) repeat fixed top right; }

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Here you Go  this is the right one, This one works I tried it on my page.

#main_body{background:url(https://img1.dreamies.de/img/819/b/5fq1poy3pqv.gif) repeat fixed top right; }