Yup, that did it, I noticed that the shuf command at the command line didn’t return a error so I figured I was wrong but had already written the above and hadn’t gotten around to editing it. sudo cp $(shuf -n 1 -e /home/pi/RetroPie/splashscreens/*.png) /opt/retropie/supplementary/splashscreen/retropie2015-blue/splashscreen.png
I also noticed you used the 00_random_splash directory instead of the one I listed above. I know I changed my default screen once so it could be that I’m wrong with the directory, but I’ve posted the one that worked for me just in case.
Thanks for the help!