u should have ur firmware as a .bin file.
then u can open it with
this little tool.
with it u can view all the images inside ur firmware.
best way to edit them.
is extract the images,
then edit them.
and exchange the old image with the edited once.
(all possible with this tool)
then u just need 2 upload the firmware again.
no bat needed.
but if u extract ur firmware, dont forget 2 repair it with the repair.bat