The old standard was Retrospect, this was in the days when it was still cool to buy tape drives for desktop computers, so tape is one of the backup methods available therein.
I believe Retrospect also allowed for you to put data on things like Syquest cartridges, Zip when those were invented, external hard disks, and maybe even floppy diskettes.
One thing to note is that imaging full computers is a kind of recent phenomenon, based mainly around the fact that fast, large network and USB/Firewire storage has become incredibly cheap in the past decade. In service of that, I do not actually know if Mac OS 9 and lower will image their own boot volumes using Disk Copy, unless of course you put disk copy on a boot CD or network access floppy. In the olden days, backups of data areas plus configuration files were often considered enough (both for speed purposes, so the backup utility didn't have to bother with the OS, and to preserve tape and other media) and if you needed to restore, you'd install the OS, do super basic machine config, install the backup utility, then install your other apps, then restore the data. (Incidentally, this was the procedure for restoring backups of servers and client PCs using veritas/symantec backup exec until super recently. I believe BeX 2012 is the first version to do a full system state backup which you can restore using a boot CD and either disk, network, or tape media.)
If I were to set all of my stuff up again, most likely what I'd do is set up a virtual machine with Windows NT 4 and Services for Macintosh enabled, with a large virtual (or physical, it depends) disk and establish folders for each retro system I was backing up, something like (from the windows/smb side) \\ntbox\macbak\q840av and \\ntbox\macbak\lc475. I'd then either do a weekly boot to a network access floppy to image the disk (because I really do like system state backups, and it hsould be deceptively simple on system 7/8/9) or use retrospect to automatically copy data to the backup location intermittently.
To backup my modern laptops, each one has Acronis TrueImage installed (I loves me some system state backups, did I mention that?) and they work over the network, putting their stuff on my server, which has a 10TB data volume, a large proportion of which is in use on the \\tect\lapbak\ share. The server's boot/exchange/sharepoint disk is backed up onto a rotating pair of 750GB external drives, but I plan on beefing this up (and adding a plan to back up the data volume) sooner rather than later. Incidentally, 2TB RDX cartridges can't possible be launched soon enough.
