Icewm knows several locations to look for configuration information, themes and customization; put together these locations are called the resource path. The resource path contains the following directories:
user's personal customization. This location can be customized by setting the $ICEWM_PRIVCFG environment variable.
system-wide customized defaults
compiled-in default directory with default files
The directories are searched in the above order, so any file located
in the system/install directory can be overridden by the user by creating
the same directory hierarchy under $HOME/.icewm.
To customize icewm yourself, you should create the $HOME/.icewm directory and copy the files that you wish to modify (preferences, winoptions),from /etc/X11/icewm, /usr/share/icewm or /usr/local/share/icewm and then modify as you like.
To customize the default themes, you should create the $HOME/.icewm/themes directory and copy all the theme files there and then modify as necessary.