Is it possible to change the banner of an iso? I successfully changed the title and notes of an iso using a hex editor but I do not know how to change the banner. Any advice?
It's possible. I would assume you could edit the cache that Dolphin has (or hack Dolphin itself to display an image of your choice). Another way would be to edit the banner data on the ISO itself. Here's a good start for info:
http://hitmen.c02.at/files/yagcd/yagcd/chap14.html
But of course it's would be best to look through Dolphin's source code for a more complete reference.
you can use GC-Tool to replace banners in GC iso's iirc
Unfortunately it is a wii iso.