If you have screen 4.3 use 1355 logo.bin

If you have screen 3.5 use 2x5 logo.bin

In inventory page you must look for number splash (nuvi 1300 is D1340-00)and write it to paper.
With hex editor change number in logo.bin to your number of splash screen.
With gir editor change picture and calculate checksum and save.
With rgn tool use your original boot.bin and add logo.bin and save to .rgn (eg.082501000490.rgn)first four numbers is your bootBLK number(HWID)last three is your curent firmware number.
Flash with updater.exe.