also, in the reverse, if you have an object dock icon that you like enough to include in your icon package, (for me it's usually thunderbird and firefox because most ip's don't include them) you can edit the png in icon developer and save it as an icon. Also nice , you can recolor to match whatever ip you are using.
 ooops, didn't read the last line... I guess if you don't use Iconpackager that tip is useless. sorry!