Copy the ftr file (which designates properties and icons of files with particular filetypes.) in /usr/lib/filetype/local.
Please do not forget to make changes to the ftr file accordingly to your system environment, such as tag id numbers.
For detailed information regarding filetypes and tag numbers, please read here (SGI techpubs).
Copy the fti files (the actual icon image data files) in /usr/lib/filetype/local/iconlib.
# cp *.ftr /usr/lib/filetype/local
# cp *.fti /usr/lib/filetype/local/iconlib