I just picked up the Firebase tonight and am looking forward to building this weekend. My plan is to mix in some green camo bricks i've gotten from True Heroes sets to give it a more camo look as well as have extra bricks to work in the two cannon towers from the Containment Outpost Patrol sets.
Although this would be a good chance for Mega to release boxes of blocks to match the Firebase sets to make it easier for other builders to add on to their Firebases. That would go along with the belief that customizing is the best part of a builder and collector.