The default resources that come with MapTool are located within the .maptool directory that is below your user directory.
C:\Users\<username>\.maptool\resource\Default\
C:\Documents & Settings\<username>\.maptool\resource\Default\
~/.maptool/resource/Default/ or /home/<username>/.maptool/resource/Default/
~/.maptool/resource/Default/ or /home/<username>/.maptool/resource/Default/
Note: You should NOT place your own resources within this directory, or they could be deleted.