Others have brought up the Office 97 style for good reason. Everything has an icon, on an icon toolbar. Every command can also be on a file menu but most of them there don’t have an icon. The ones that do are special or intended to draw your attention.

And there’s a consistent metaphor: for example the web browser is represented by a globe for the world wide web. So the “hyperlink” function is a globe with a chain. This the “preview as web page” is a globe with a magnifying glass (whereas the print preview command is a sheet of paper with a magnifying glass.).

This icon language hints at function through its form and helps serve as a cue, a reminder, or a visual representation of its function.

And it all worked on 640x480 256 color screens. They are thoughtful and useful. These plain flat uninformative icons are just rude.