How can I add custom borders?Make a file called "p8173_ownbgs" (no extension)
Use Notepad++ to edit it, Notepad and Wordpad mess it up. It should contain the following. You also need to enter down to line 2, or the file won't work and you will soft-brick your SNES.
overmount /usr/share/backgrounds/
Now FTP in, copy the backgrounds folder to your PC from /usr/share/ and reupload it to /var/lib/hakchi/rootfs/usr/share/
The file you made a moment ago needs to go into /etc/preinit.d
Restart your SNES Mini and if all went well, it will be using the new folder, which is writable.
So on the PC, just create new folders following the examples set by what you see. Best way it to copy a folder, rename the files, and edit them with your favourite Photoshop version. Here's what my SNES Background folder looks like: