Not a bad effort at all, IMHO. Always time to learn and grow as you go along.

One suggestion I'll pass on from winter dioramas I've observed over the years. If you can 'drift' your snow -- as though a stiff winter wind is whipping it and piling it up in a particular direction -- it helps elevate the image in the eye (and mind) of the observer from 'static' to 'dynamic'...which always helps 'sell' the illusion. In Youtube vids I've seen, it might be as simple as propping your base up at a slight angle when you apply whatever snow product you're using. (That would obviously apply more to powders than paste. )

Anyway, great job, and keep at it!

Looks good to me! It's making me cold looking at it and that's what you want! 

If you want it deeper you probably should make the 'snow' out of plaster or stryrofoam, whatever and then sprinkle the molding paste over top of it. 

I really like Greg's suggestion, I've stealing that for my own dios. 

Superb! Very convincing dio!

I think that looks very good. You might consider using model railway scenic "snow" as a light coat in a few places to make it glisten. As for snowdrifts, you could roughly scuplt styrofam and then coat with spackle, glazing compound, Durham's Water Putty or acrylic artist paste. Then paint. I have used a thick coat of acrylic white primer as snow and ice and it worked out for me.

Fine looking diarama and very interesting tips to boot.

Beautiful diorama KeithRob!  I like the snow buildup on the tracks and wheels, the rust on the various tank parts, the dried bushes, the barbed wire.  Very realisticc looking.

Hmmmm!

     I don't know. You seem to have done a fine job to me! I like the snow buildup in the treads and on the tanks deck. Nice job overall for the first one .Now what dio is next?