I don't think there is an ISO rule for icons, but there definitely are some 'standards' for Desktop applications.
Size-wise, Windows .ico icons range from 16x16 to 48x48 (pre-Vista), up to 256x256 (post-Vista). Mac OS X .icns icons go from 16x16 up to 512x512. Favicons for web have to be 16x16.
There are some naming agreements as well, they have to be composed of US-ASCII characters, and the dash “-” is used to separate levels of specificity (edit-copy, edit-cut, edit-paste).
But I think every program has its own conventions. For example, Symantec follows this one. While some of them are more or less common ground ("Color icons indicate objects that are in a healthy, running condition. Gray icons indicate objects that are offline."), specific functionalities follow their own internal rules.