Very nice indeed. One question which color did you use for the sandbags? I thought they are some kind of buff color in reality or am I wrong.
I went with a sort of greenish grey base (40% basalt grey 60% german cam. dark green).
Here's some of the ref pics of FSB's I found online:



It contrasts quite nicely with the ground colour, and you can add washes to tone it down/filter it.
I did go with a more hesian colour for the bags on tanks/armoured vehicle's as otherwise the'd blend in with the colour of the armour.