I also noticed in the first pics, that the light source seemed to be coming from two directions.
The B&W photos look better, since the light source discrepancy is not as noticeable, at least to me.
The tank looks great, nice smooth build, yet I think a bit of dust or dirt in the tracks and lower hull may help it to look more 'at home' in the fields you've chopped it into. On the first pic BTW, nice effect putting the grass in fromt of the tracks like that! Well done!
Keep up the great work!