When you run clrmame on mame.exe it can make a dat with the crc for the roms. When you need to scan pictures you have to use a dat someone else made that has the crcs. You'll see a dat come inside picture packs. You can't make a dat for flyers with mame.exe because it doesn't know the crcs. When you scan picture folders with the premade dats you call them "roms directory" in the Settings menu. It's not intuitive or whatever. You have to use tutorials and figure crap out and then remember it and it becomes easy to the point where you don't even have to think about it.