for first, download all necessary for this proceeding.
Download all files on my drive: http://ziomirko.altervista.org/Paper_Mario_Yay0_utilities.zip
You can find: gedecompress, N64RIP and szp.exe.
Extract all files in a folder. Open "Gedecompressor.exe" and select in the list of games, Paper Mario (press P).
Now, load the Paper Mario Rom. This program will make a lots of .bin file. Select the bin of the texture you want to replace. I replace the "Press Start" text, in this case it's the file "27DA76C.bin" in 1290 offset. With N64RIP we export
the original texture. Modify it as you like. When you finished, import the image(THE IMAGE DOES NOT MUST BE HEAVY of the original) in the .bin file. Move the .bin file on szp.exe, and download a hex editor (I recommend HxD), and go to the "Press Start" Yay0 block in the rom. Open the bin converted in szp on HxD and copy the content. Paste it and delete the original. Now, if the file is smaller (the bin file) than original, do this step: use the calculator, and see in properties the details, and see the bytes, and do original - modified filesize of bytes x 2. Add as many zeros as result of this operation. Now, you can view the "press start" modified texture in your rom.
-Tribute to Robinerd-