Third (your use case), you would like to use the default theme but you want to do some additional processing of the splash.svg file. live-build, as far as I know, does not provide an automatic way of doing what you want. But you can take advantage of live-build's increasing flexibility and achieve your aim relatively painlessly. Pointing you to the binary_syslinux script I think I gave you the hints to achieve your goal. You can use a similar method. I would use, like I told you in my previous message, a binary hook. Once all the syslinux files are in place (and have been processed by live-build) you can run your binary hook which should be capable of performing the following steps ( You already succeeded changing the icon, so I'm skipping that part): 1.- copy the splash.svg file from ../config/bootloaders/isolinux/ to isolinux/
2.- Use sed to make the substitutions you wish "s|@PROJECT@|YOURPROJECT|" and "s|@VERSION@|YOURVERSION|" and so on and so forth... 3.- Finally, convert the isolinux/splash.svg to isolinux/splash.png And be happy with it. It is as easy as it seems :)
Sorry for the long message (again) but I try hard to explain things as carefully as I can. I do not know if I'm right or wrong. I'm trying to give you ideas and options for you to experiment with. Have lots of fun and a really great weekend!