Manny, the layout looks fine, the figs are great, the tank superb, but the bricks need mortar, and the best way to do that would have to be a light tan oil wash. White+raw umber+ a pinch of yellow. Apply it as a pin wash. You won't even need to "ruin" the rest of it. And if you get a little bleed-through, so what--a lot of the best results I've gotten have come from pure mistakes. Stuff you couldn't repeat if I tried! Give it a shot!
First though, I would paint the building's bricks in a color to match the rubble--and not, NOT all of them, just about 40%--and then paint some of the rubble to match the bricks. YOu'll get a much nicer ditribution of various colors there, without any monochromaticism.
Don't forget to add some "mortar color" to the sides of some of the brick rubble too, to give it even addt'l realism.