Remotely Change Splash Image

For future reference - probably not. From Issues · balena-io/docs · GitHub

we encourage any user to go and replace that logo with their own. All you have to do is replace the splash/resin-logo.png file that you will find in the first partition of our images (boot partition) with your own image. NOTE: As it currently stands plymouth expects the image to be named resin-logo.png.

Balena docs:

If you would like to replace the balena logo with your custom splash logo, replace splash/resin-logo.png located in the boot partition of the image.

Changing that file is the normal method and makes sense: how else to edit a file on the boot partition. I would not expect different, valid contents of a .png file to cause the boot to fail, not that this sort of update sounds like one anyone should do repeatedly.