This is quite low priority as it'll only be noticed by developers and others who have the AppleShowAllFiles preference set so that they can see hidden files in Finder.

This means that I/they see all the hidden folders (eg. .background, etc) added to the DMG scattered seemingly randomly within the DMG window!

I would be a good idea to position these hidden directories out of view by default.

Check out this bug filed for DropDMG for the same reason.