I designed a downloadable card Bunker for Hour of Glory - a lot of the wall texture and details would be useful for any project like this and it saves painting too... I did a lot of research on war bunkers and used a lot of photo evidence and visited as many as I could - I hope it's helpful? Obviously this would only be useful for an underground HQ bunker complex...
http://www.wargamevault.com/product_info.php?manufacturers_id=2491&products_id=58243