This article and slide shows show iconic parts of Mac OS starting in 1984 through the Mountain Lion announcement.
The slide show is in 15 parts starting with a slide with screen shots from 1984 and from 2012:
It continues with a shot of the 1984 showing an open window. Then a shot of the Clarius, the dogcow. Followed by the smiling Mac icon. One of the slides I wouldn’t have expected is a shot of IE running on a Mac OS 8 screen. There is also an About This Computer window of Mac OS 9 from 1999. Of course that is quickly followed by a 2000 screen shot of Mac OS X from when it was unveiled that spring. The final slide is of a series of Mac OS install CD and DVDs starting with System 7.5 through Snow Leopard. So that would cover all the CD releases since future OS X updates will not be distributed on disk.
See the Mashable Tech article at: http://mashable.com/2012/02/17/mac-os-timeline/