Cisco says:
Cisco icons are globally recognized and generally accepted as standard for network icon topologies
However, some of those icons are very misleading, see for instance:
So I hesitate to use them in documentation, and find it hard to believe that they are a standard.
Is it really the generally accepted standard icon topology?
Or are there more up-to-date sets? (by another vendor or a community/standardization effort)
I NEVER use Cisco icons, choosing to use realistic Visio shapes depicting actual device/card layouts that you can get for from from visiocafe.com.
As Chopper said, Visio shapes are much better than Cisco icons. (I have yet to see a handheld that looks like a microwave.) In addition to visiocafe.com, Microsoft has a number of visio stencils available for download.
At least as useful as those Cisco icons is this set of widely accepted standard symbols... (although it seems to be missing DASD.)
There isn't really an accepted standard for icons. The Cisco icons themselves have changed substantially over the years based on rebranding, acquisitions, new product lines, etc (and will absolutely change again). Being consistent with icon usage, including legends and clearly labeling are each as- or more- important than the icon itself.
A well thought out selection of boxes and circles with appropriate labels and some kind of consistent flow is infinitely more useful than a jumbled collection of images from a stencil.