Sorry for bumping an old topic, but I too am having this issue when trying to load Naomi GD games, and I feel like I have followed every setup guide correctly. I have been successful loading regular naomi, atomiswave, and cave games in DEmul and have run other chd games like SF3 and KI2 in Mame just fine, so I'm really stumped as to what I am doing wrong here!
In my roms folder for DEmul, I have the game .zip, a folder with the same name as the game with the chd inside of it, and the naomi, naomi2, and naomigd bios zips, but when I try to load a naomigd game, I get an, "unable to find 317-####-jpn.pic" in romset ****. My only idea of what might be wrong is when I look inside the game zip, it says it is a .bin and not a .pic?
Thank you for your help!