When a drive has been accidentally overwritten you will need Data Recovery Tools to restore the remainders of your data. After unpacking an image on your drive those parts of your drive where data were written are definitely lost and can not be recovered.
By installing testdisk you may be able to recover parts of your files.
Included in the TestDisk suite you will also find the tool PhotoRec that helps to recover individual files even in the case the partitions can not be restored by testdisk or the drive itself has a hardware defect.
TestDisk/PhotoRec can also be run on a backup image of your drive (strongly recommended).