This program will take practically any image you can throw at it, and write it to the save game of your choice (must be decompressed)
lba2i2r <input_image> <input_save> <output_save>
Simple as that, provide it a valid image, provide it the save you wish to write the image too, and tell it where you want to save the altered save with whatever name you'd like.
My save decompressor should cover altering compressed saves, as this program isn't designed to work with the compressed saves.