Change Plymouth Splash Image?

This may or may not be Prometheus-specific, but can I change the Plymouth splash screen without installing a new Plymouth theme and being limited to the image it uses? I’ve replaced /lib/plymouth/themes/NetrunnerPrometheus/background.png with another image, but it is not used.

Plymouth is started very early in the boot process. Actually before the root partition is mounted. So you need to update your initramfs for the new bootsplash to be taken into consideration.

sudo update-initramfs -u is the command that needs to be run to do so.