Here's a quick update from the model i posted earlier this morning, after some debate I've finally decided on a basing style for the dark angels. The proportion of large bases will allow for some creative basing that can really be showcased throughout the army.
The concept here is broken overgrown asphalt, i may add further debris in the future, but for now it's a very "nature overtaking society" look, with the nice greens protruding from the greys and blacks. The chunks of asphalt are made of pieces of ripped cork board, which you can find at most craft stores. I've had this stuff hanging around for awhile so i've finally decided to use it.
Gravel and sand is then applied to even out the texture of the base, followed by a relatively limited palate of colours.
Finally GW Static Grass and Woodland Scenics Tall grass was then applied to represent the vegetation growing between the cracks.
Other possible additions to the bases could include oil spills, water, and spent shell casings.