Is there a "mother of all images"?

Most of the time the latest hardware that is released has an image that will work on all the other hardware.
However, some times like when they released two new hardware platforms at once, MBA, MBP they had independent images that would would work on older stuff but you had to have the proper one for each of the new platforms. Most of the time the next Combo Updater will solve that issue but that is not guaranteed, as much things will Apple are not guaranteed, we will release no new hardware this summer and the 4 weeks later a new MBA existed, etc. I have not seen an Apple person that has come out and say the old way of imaging is still the right way, but, we have been testing that old method and it seems to work still. just make that first image so its never booted, you can use instaDMG or do it manually and you should be fine in my experience.

Rule of thumb I use is if a computer comes out during an OS cycle, it will need its own image. Once the combo is released then all is good!

http://support.apple.com/kb/HT1159

Look up the "Original Mac OS X included" for a specific model of machine. If you have the same version of the OS, most likely the hardware will require a specific build of that version to run. People often refer to this as "forked".

This isn't set in stone and not guaranteed to be true in the future. But, in general, later versions will work on all machines that originally shipped with earlier versions. 10.8.4 will work on all systems that came with 10.8.3 and earlier, provided the system meets hardware requirements for 10.8.

Right now, the Mid 2013 MacBook Air's have a specific build of 10.8.4 and require their own image. After 10.8.5 comes out, a new image with 10.8.5 should cover all Apple hardware (until new hardware is released that ships with a special build of 10.8.5).

... ahhh... yep. We also try and use the newer hardware and the latest combo to cover the widest amount of machines. However, Apple is apple and they do what they do. So sometimes you get forked and that's the rest of the story.

The one that came with your Mac.

Honestly, that seems to be the only correct answer. True, you probably can take the base image that you get from the latest new hardware release and build your base image on that, and boot everything you support, but as previously mentioned, there are no guarantees. I seem to recall that when two models were released at the same time, the higher build number did include the drivers for both systems, but that's just my memory. Don't trust it.

The point: use the OS that ships with your Mac, and just add your application stack and manage the settings you care about. If you truly need to rebuild a system, do an Internet Recovery. Now, I don't practice what I preach here for one simple reason: we have a proxy, and Internet Recovery doesn't work with proxies. I have to keep up a base image that boots all of our systems, and if we encounter a fork, I'll potentially need two.

JPDyson's right though. Never trust that an OS will just work! While using a thin-imaging approach with internet recovery is probably the "safest" approach as JPDyson mentions, it's slow. If performance is a concern at all you're going to end up making base images. Here we support something like 22 models of Mac that run 10.8. I've got a single Base OS that covers all but the newest MacBook Air. So... two base images at the moment. I do keep around a base image for 10.7.5 and 10.6.8 just in case, but they are unused.

I use this method:
1. capture the factory DMG for each new model that walks in the door
2. provision new models by thin imaging
3. when it comes time to reimage a Mac, I have a reimaging script that uses ASR to restore it to whatever DMG I made of it when it first arrived, IF that DMG contains the latest production OS. If our production OS is NEWER than what the Mac originally shipped with (i.e. 2009 iMac and OS X 10.8), it gets the latest DMG we have.

The logic in my reimage script uses the Macs model identifier to determine what DMG gets restored. You'd think I'd have to keep a huge stable of DMGs this way, but since we tightly control what models are purchased, I only ever have about 4-5. Currently we have images for the 2013 iMac that get applied to the 2013 iMacs and anything earlier, a (cringe) MBP Retina image, a 2012 Mac Mini image, a 2012 MacPro image, and a 10.6.8 image for legacy support.

Just an idea but you could use 'thin imaging' so you use the OS that comes with the kit and script, package, whatever in your Casper builds so the outcome is how you like it. That way you don't have to worry about keeping your images up to date, on the bleeding edge. Obviously you don't erase the original disk in imaging.

This way you can occasionally update your base image when needed for mass OS rollouts or for reimaging unwell computers?

Don't use this myself but very interested.

As others have said, use the 12E55 build of 10.8.4. This will work on every current Mountain Lion-capable machine save the new MBAirs.

Realize that anytime new hardware is released, there is a custom build of the OS for each new computer model (the KB article with the specific build numbers is referenced above). So long as you know/make it aware that *new* models brought into your org may require you to have access to the device first (to copy the base OS image), you're probably good.

As others have said, eventually the OS becomes "re-unified" although that may or may not be the next numerical version...

We test the thin image idea and ended up just ditching it back to our InstallESD modular/compiled image. The images only get forked maybe 2-3 times a year so its usually not a big deal but when it does happen I check here first to see what others are doing compared to what I have planned.