I used a sculpting tool to scribe the edges and the cracks and a stiff plastic brush to add faint lines to the foam surface:
To finish off I added some 10mm Heki Autumn grass along the edges (as well as more shrubs) and poking through in a few spots in the concrete.
A few more items to be added. I am going to go through my collection of odds and sods and see if there is anything I can use for some scatter terrain: old barrels, pieces of scrap steel, lumber that sort of thing. I also have another structure in the post from Sarissa Precision and resin pick-up from Warlord that will get turned into a derelict vehicle. A few 60mm bases with taller shrubs/small tress might also find their way onto this table.