The logos are .big files which are stored in a .viv file. You can use EAGE to extract the .big files from the .viv, then use DOLFFIN to export the logo .fsh files from the .big files. You can import to and from the .fsh files using FshX. You can use GIMP or Photoshop to manipulate the files which you're going to import.
Basically, it would go like this:
- Using EAGE, open logos.viv (located in the fe folder)
- Extract the .big file you wish to edit. The name of the .big file indicates what kind of logo it is and where it's used (eg large, medium, pause, score etc)
- Open the .big file that you've extracted using DOLFFIN.
- Extract the .fsh file. This is the logo art.
- Open the .fsh file using FshX. Export the texture as a .dds file (Direct Draw Surface)
- Open the .dds file in GIMP or Photoshop. You'll need a plug-in to do that, which you should be able to Google.
- Replace the logo art with a new logo that you've sourced. The important thing to remember here is that you match the dimensions and positioning of the old logo; in other words, it must be roughly the same size as the old logo (if you were to draw a box around it) and placed in the same spot on the canvas. When you're done, save the .dds file.
- Now, you reverse the export process. Open the .fsh file using FshX.
- Import the updated .dds file into the .fsh file and save it. It's important that you save the file in FshX or the change will not be retained.
- Open the .big file using DOLFFIN and import the .fsh file. Make sure you've highlighted the .fsh file within the .big when you click Import Blob in the menu.
- Place the updated .big file in your sgsm folder. The game will now load it instead of the .big file contained in logos.viv.
- Start the game and check out how your logo looks in-game. If it looks right, then you're done. If it's not positioned correctly, too big or whatever, then you'll need to go back to step seven and make some alterations, import it again and re-check.
That's a basic overview of how it's done. Give it a shot and let me know how you go or whether you've got any further questions, perhaps I can flesh it out into a proper tutorial.