Apple should provide "generic" icons for applications, files, plug-ins, and toolbars. The old designs for OS 9 were simple and left plenty of space for customization, but the new default OS X icons are too busy and cluttered.
There are no sample toolbar icons at all, and the current ones (in Finder, AppleWorks, and Mail) are inconsistent. This is why developers have to roll their own, and why we get lots of ugly meaningless icons.
Apple wants developers to use standard menus and windows, so they provide tools like Interface Builder that create them. If Apple wants developers to use standard images they should provide them.