Everyone wants to have users download a small .dmg file from their website. Opening the dmg pops up a window showing a pretty background, the application's icon, and an alias file to the /Applications directory.
Finder in 10.6 creates non-backward compatible .DS_Store files, so to get the positioning and background image, you need to create a dummy dmg by hand on 10.5, copy its .DS_Store, and save it for copying into your production dmg.
No-one wants their dmg to have a .Trashes directory, and no-one wants the mounted image to have free space -- it's just wasteful, and it feels unprofessional. The key to creating just such a dmg is to populate a local directory with everything you want in your dmg, use hdituil to makehybrid from it, and then convert to the desired format (probably UDBZ format with -imagekey bzip2-level=9 for maximum compression).
If you have an SLA that you want to display, you can unflatten, add the rtf SLAs using Rainer Brockerhoff's AddLicense tool, and then flatten the dmg again.
