I added rivet detail to them in exactly the same way as I did the walls and painted them to match. With the doors, I didn't like the laser etched pattern so opted to paint a simple chevron pattern over the flat surface sides instead. I think it gives it a more 'sliding shutter' look. I also added some graffiti decals from Warlord game's Dredd range. I think they were free in a copy of Wargames Illustrated. They fit the bill anyway.
Overall I really recommend the Hive Terrain products from Art of War Studios. It's a little pricier than TTcombat and others, but I honestly prefer the aesthetic and they are a joy to put together.