Try
Wiimms ISO Tools.
Download and extract Wiimms ISO Tools, then copy your image to the "BIN" folder within Wiimms ISO Tools.
In the "BIN" folder click in the adress bar, type "cmd" and press enter.
In the now opened Command Prompt type "wit extract game.iso DUMP" (replace game.iso with the name of your Iso-file; if the name has a space, you'll might need to enclose the name of the file within '' like 'some game.iso'). After a few seconds there should be a "DUMP" folder within the "BIN" folder, containing all the game files.
Now just replace watever files you want and then go back to the Command Prompt.
Type "wit copy DUMP patchedgame.iso" and hit enter. After a while there will be a new, patched, .iso in the "BIN" folder.