This looks simple enough. I looked at your RUNME.sh script, and it looks like it should work.
I was hoping people would add status messages to the eink display WHILE their RUNME.sh scripts are running (to provide feedback to the user that he did it right). This s WHY I published that particular demo RUNME.sh script that does the pretty pattern and text. I did the "eips -p" to display the pretty pattern, just to make it *obvious* that the RUNME.sh really did run.
You can copy and change stuff from my RUNME.sh (which you can download where you got my data.tar.gz), and add eink display messages to your RUNME.sh script. I suggest adding messages for "Already installed" and for "Now copy screensaver images to /mnt/us/screensavers" (or whatever works for you).