Fortunately, Google Images will almost certainly turn up something that you want. For example, I wanted an icon of the El Capitan “X” logo for my SSD, so I searched for “os x El Capitan” and then ...

One of the standout features was the Dock, which was introduced in Mac OS X 10.0 Cheetah. The Dock didn’t always look the way it does now; at first, it was just a row of plain square icons.