1. Open the EBOOT.PBP (in the folder WITH a %) that you want to alter .
2. Extract PARAM.SFO
3. Find your custom ICON0/PIC1
4. Create a New EBOOT.PBP using PBPUnpacker... use the PARAM.SFO file from earlier and the new ICON0.PNG and PIC1.PNG
6. Save the new EBOOT.PBP in the proper folder with a % and you're done!