the open command launches to the default GUI application in the default window manager
in terminal.app the default parent GUI is your home machine's quartz display manager.
from remote, you have no parent GUI...unless you are in a xsession through vnc or the likes.
you are calling open "disk image file" which should launch Disk copy.
the same functionality is availble from the command line with some combination of hdid, hdiutils, and mount. read the respective man pages to get a clue.
then you can mount your image and navigate to th image by
cd /Volumes/"name of your image volume"
