I didn't add wbfind.
In retrospect, icon.library is a good idea to have in the ROM. I've ran into situations when a piece of SW would have needed it and I didn't have a hard disk + WB installed yet.
Perhaps I'll build another set of ROM images with it included.. I'll just have to test whether the 3.9 icon.library works with wb3.1, or whether I need to use the old one.