To mount the ISO image file.iso to the mount point /media/cdrom use this :
$ mount -o loop -t iso9660 file.iso /media/cdrom
9.2.2. create iso file from CD
$ dd if=/dev/cdrom of=isofile.iso
$ mkisofs -V LABEL -r /mnt/cdrom | gzip > cdrom.iso.gz
mount iso file
$ mount -t iso9660 -o loop cdrom.iso /mnt/cdrom