There's no "generic file name", but most of the backups you can find are made with DiscJuggler (it supports multisessions, like DC selfbootable games). So that's CDI files.
But every files used as 1st file read are named *.bin (1st_read.bin, 0winceos.bin, ...). You might want to patch these particular files and then remake your game using Echelon's tutorial, for example.
That's true : I should have included the possibility to open any file (could be usefull for Nero images, for example).
It will be in next version of PAL Patcher.
If you want to patch your game with PAL Patcher, either make
an image with DiscJuggler (so you'll get a CDI file), or try to patch your 1st_read.bin and then reburn your CD (less easy).
I would recommend Yamaha or Plextor burners, but I think Liteon ones are cheaper...