Simply remove the NewIcons patch from s:user-startup, then you'll no longer see the new icons. They'll still be stored in the icon files but you won't see them.
If you also remove newicon.library from libs: no other program will be able to load the new icons, either.
Im gonna attempt installing OS3.1 over my current install
This won't help. User-Startup and third-party libs are not touched by the installation script.