Hi Jason,
First off, that is a very, very good first effort. The construction, painting, and groundwork are all technically good. The first thing that struck me was your figures--they look too good for a first attempt. The second thing that struck me was the tank--it looks too "green". The third thing was the groundwork--just well done. When I read the rest of your post it all made sense, perhaps because I took a similar route into armor (fantasy figures, then card models, then plastic armor).
I suspect you do fantasy figure painting, primarily because of the tank. The palette of greens looks too green, like something I would use for a goblin. The current trend in fantasy painting is to use bold colors, even to the point of using florescent colors for highlights. The trend for military vehicles is to use a much more subdued, earthy palette. Shadows, highlights, and contrast are still highly desired, but with more subtlety. Earth tones rule--raw sienna, burnt sienna, umber, black, earth yellow, sand, ivory. Of course, a lot of really great models break this rule by juxtaposing drab colors with bright ones (i.e., sticking a bright red flag on the deck of a drab gray vehicle). You should be a natural for exploiting that.
Next time, I recommend lightening the green base color on the tank with earth yellow or armor sand instead of bright green or white. For the tracks, throw lots of earth tones at them using washes, pigments, drybrushing, and/or sponging. Tracks pick up dirt and rust very quickly, especially in a wet environment.
Good luck with this new branch of the hobby and if you have questions, do not hesitate to ask. There are some really great modelers here willing to help anyone who asks.
-Doug
