Another "thinking out loud" post for you Timberwolf! I hope you understand Im not trying to nit pick your work...... just offer some thoughts that you might want to consider.
With the tank being so dirty, I think the ground work should be softer. What i mean is more evidence of heavy tracking, especially behind the tank.
An easy way to show this would be to raise the sides and between the tracks with some polystyrene trays (as used in packing meat) or cardboard about 0.5cms. Then cover agin with your method. Use the tanks tracks or some others to leave a print behind or several all over to suggest traffic. The rougher the better! Little holes can be filled with light earth tainted gloss paint to show puddles ....... this really makes the ground look wet and soft. Build up in layers if deep. A little static grass at the sides and middle for some colour adds to the picture also. maybe you could bury the stones a little as they make the ground look harder as they are "sitting" on it instead of in it!
You have made an amazing tree........ this is excellent. I also like the use of the dead trees. The dirt on the tank and ground is excellent. This is something I will use. The colour is brilliant. have you added any colour or is this natural? Overall its a lovely little scene and you should be proud of your work. All the best!
After 2 weeks in the making it is finaly done, and put in a dio too 
