We constantly see broken sections of wall being used as cover and terrain in MFZ games. These can be a little bland and divorced from any story the gaming group might want to tell. Drawing inspiration from real world sources might help to make your table look better and give some sort of source for the game story. A friend of mine sent me this link to pictures of an Armenian ghost town. I figured I'd share it with you and see if might help inspire some people. While there are some broken down buildings, there is a context to these ruins and not just random wall sections.
Moving on to something a little more urban, here's an article about abandoned malls. Some of the external locations could make good game backdrops. Also, depending on what scale you play at, you might be able to squeeze your mechs into some of the inside locations as well.
I hope the pictures in these articles give you some ideas for new terrain for your gaming table.