I just posted some better photos of my walls (and some of my WIPS "accidentally"!). The walls are nothing but a simple metal equipment case dividers stuck to some cork and painted. Those cases used to be popular for transporting miniatures around here and I bought one myself - I later invested in KR case instead and I am really happy with that one. They dividing walls come in three sizes. I didn't bother cutting them or anything, so I got two long sections, one medium and two short ones. They come just a bit over 3 feet long combined.
As much as I'd like, the idea is not mine. Guys at our club used those to make terrain for WH40k, but I don't know if they came up with it.
I gave them a coat of PVA to seal the foam they are made of and sprayed them black, then drybrushed them with greys. This was a great opportunity to paint some graffiti on them, but I unexpectedly ran out of ideas very quickly. I settled for some shameless advertising of the people that helped me bring my moderns project to life in the first place.
I left other sides blank - the idea is I'd use them for military base and I'd want at least one side to look "professional" :D.
Below is a "scale" shot, with one of the crew members I keep showing. As you can see, he will get a helmet, too. Looks like finished conversions weren't all that finished after all!
Thanks for looking,