I too am having trouble with background images and auto-open (atleast a folder, as I understand it will not auto start on mac os x). I have been successful with creating a custom icon when the disk is mounting (not successful in creating a badge on the dmg icon). However I would really like to add a background image and have a folder auto open when the disk is inserted.
I have tried to follow the directions by making sure I am linking to the image saved on the disk, burning as a read only etc, but no hope. I’ve also created an empty folder and deleted it
My disk utility is set to auto open read only discs, and I have Auto open image window after mounting selected in preferences on DropDMG.
Have tried burning folder with DropDMG and Roxio Toast 6.