As each windows version localizes the "Program Files" folder in a different path, is not possible distribute a material library that mtch all windows installations installations. Because that, the maps paths bust be configured in 3dsmax in order to find them.
What is important here is to add the Forest map path to 3dsmax, using "Customize->Configure User Paths->External Files". By default the plugin does this automatically the first time it is used interactively, but not in the slave nodes. You must add it manually, or copy the images to your own network map path.
If you can't run 3dsmax interactively in the slaves, the map paths are defined in this ini file:
C:\Documents and Settings\<username>\Local Settings\Application Data\Autodesk\3dsmax\<max version>\enu\3dsmax.ini
See [BitmapDirs] section (you can copy it from a installed workstation), be careful what some folders on this path would be hidden by Windows.
We don't include this path automatically from the installer because some technical issues. However, we will try to solve this issue in the installation for slave nodes in next versions.