I need a flame retardant, spray-on product that will allow me to give
an artificial Christmas tree a "snow covered" look.  I've tried many
"snow in a can" type products, but all these products seem to do is
turn the needles on the tree white (I could just use white spraypaint,
and pretty much get the same effect!)  What I need is a product that
will create big, chunky, dimensional patches of snow.  During the
Christmas season, Treause Island stores sell artificial trees that
have this chunky snow effect applied to them, but I don't know how
they acheive the effect.  Ideally, I would like my tree to look
something like this:

http://users.triconet.org/jaboeck/April/P4220001.JPG

Thanks for your help.

This stuff looks promising to me, but I can't vouch for it personally:

http://www.stevespanglerscience.com/product/1262

I once worked in construction, and once we were putting light texture
on drywall before painting, and it was white fluffy/chunky stuff. I'm
sure you could find some at a hardware store. It could probably easily
fall off though when you put the tree away. I don't know exactly
what's it's called. Some type of spackling. The guy used a machine to
spray it on though.

In line with purkinje-ga's comment, you might find that you can
use textured acoustic (popcorn) ceiling touch-up spray:
http://paint-and-supplies.aubuchonhardware.com/spray_paints/spray_paints/easy_touch_acoustic_texture_spray-791940.asp

There are many brands, and your local Home Depot should have it.

sublime1-ga