I'm not too sure if you would call this modding to be honest, as operator logos are an integral part of the platform's design, although you wouldn't think so by the amount of cr4p Nokia have put in place to stop us!!!
I have a few questions to discuss, if you could say which one(s) you're replying to that would be great!

1) I've tried everything to gain access to the folder to place an op.logo into (C:\Private\10000850) - secman, helloox2, app trk, installserver, rompatcher, activefile, everything, including the oplogo changer apps - nokia has seemingly cut off every entrance now! My question is - these colour op.logos do work when put in that folder, so what is nokia's official method of applying these logos to the phone?

2) Is there not a way to access the private folder through any service software on the pc?

3) I have had some success with the NokiaLogo app, which sends you a logo via SMS, but that's only black and white, not colour, but when i've tried it, it forces you to use a 128x32 bitmap but the phone squashes it into a 97x25 frame on the home screen. Any ideas why?