I've been using the Oracle Workflow since 2002. The icons it ships with are pretty terrible so I redesigned my own. They should work fine with other workflows and probably other applications too. In the download pack I've included a preview, icons (.ico) and png files.
I haven't finished the full set of icons and could produce some 16x16 versions for inclusion in the executable (yes - I resource edited mine!). I also added a manifest file to my source directory to allow XP to style the toolbar, buttons etc. Let me know via the contact page if you are interested in Oracle Workflow. No idea how many people are still using it!
These icons are licensed under a Creative Commons Attribution 3.0 license.
If you can't or don't want to provide a link back, please contact ibug for licensing details.