COMMENTS ON FINAL ENTRY
The layout of this piece is unique and nicely suitable to the intended use. It suits the miniatures it is intended to display as a background, but it also lends itself to telling a story that involves the same miniatures.
I like how your overall color scheme and look match the miniatures so well. It looks like you made the miniatures and the background at the same time as a unified package.
I salute your efforts to branch out into new tools, specifically airbrushing. I have always intended to do the same, but have yet to actually take any steps in that direction. You did, and on a contest project no less.
The snow-dusted ground works well for me. The little details you scattered around add to the piece without distracting from the miniatures it is intended to display. I like your efforts to create glows of reflected light from various light sources. I like that you made modular small terrain bits to fit into the squares where you don't have pieces to display. It gives nice flexibility to the piece. The wood looks nicely gray and weathered. It surprises me just how much I enjoy the wooden stop at the end of the tracks. I keep getting drawn to that detail. It's exactly right and realistic to be there. So many others would have just had the tracks end. Those few boards really sell the entire piece to me. Well done.
As far as things that could be improved, others have mentioned the "tufts" of grass. I appreciate the stylized/cartoonish direction you were trying to take things, but they just look a little too stiff and straight for me. I find my eye drawn to them as they don't quite match the level of detail and realism you achieved elsewhere in the piece. Perhaps if you took some short lengths of thicker stranded copper wire and untwisted and painted them, it would let you keep the slightly abstract look you are going for while allowing you to put some curves and kinks into the strands.
Also, while I appreciate the effort you put into creating light blooms with your airbrush, the colors of the blooms seem a little flat/matte to me. I catch myself wanting more "light" looking colors. I'm sorry I can't be more specific as I have no personal knowledge of what to suggest. Perhaps others with more experience than me can be more helpful.
Overall, I really like this piece. It does exactly what it should, and more. If I ever get into miniature painting, you've inspired me to attempt my own displays.
Thank you for participating in this contest and sharing your work in the WIP threads. Best of luck to you!