Yes, I would like to know this as well. I get loads of album art/scanned documents turning up in my gallery. You can click on 'all images' and then 'filter by folder', 'camera default folder' to just show images taken by the camera, but it's annoying to have to do this every time you open the gallery. It would be nice if there was a way to just disable those folders completely so they never show up at all.