The rom images are placed under $installdir/lib/faumachine/roms/
To try another pc bios:

• backup the old bios

cd $installdir/lib/faumachine/roms/ cp bios.rom _bios.rom.ori

• replace the bios file

cp $fromwhereeveritmaybe/yourbios.file $installdir/lib/faumachine/roms/bios.rom

restart faumachine