Looks Great for your 1st try, and adding more snow to the vehicle really made the difference.
The best way to know what something looks like is to have many Reference Pictures of it, even if "It's" the ground your tring to recreate. This holds true for any groundcover from Snow to Sand to Cliffs or Beaches good Reference Pics can help make them ALL better. Don't try to model from memory, get Pictures.
To see how wheeled and tracked vehicles look & act in the snow and, more importantly, what the ground looks like after I found photos from the Russian Battle of Kursk and the American Battle of the Bulge. Try looking-up battles that took place during winter time, Operation Barbarossa(sp?) is a perfect example.
Also, a company named Woodland Scenics makes many model railroad groundcover products, one of which is simple named "Snow" and is a very VERY fine powder of somesort. It's easy to find, comes in it's own plastic shaker bottle, and is inexpensive. It's the best I've tried to date. Unfortunately the on bottle instructions are LITE on instructing so trial and error are the way.
And I read somewhere to paint the ground itself White in places to make melting snow look Thicker(dense) or Thinner(less-dense) in different areas tring to replicate how snow naturally melts unevenly. The White undercoat helps make the snow-layer itself look less translucent or harder to see through; it's a good optical illusion.
Just last week I bought & received a New "snow kit" to try out from a company named The Small Shop and it looks promising so far.
Again, your 1st dio. looks Great & Good Luck to Both of us in our attempts to make realistic looking snow,
-Ray
PS- Sorry if I ramble or was hard to fallow.