I realize this is an old question, but I was recently searching for this when trying to customize a 15.10 ISO. I found no other answers to this, anywhere. About 15 minutes ago (plus however long the re-mastering took so I could test this) I stumbled over the answer, so I'm going to provide it here in hopes that the reason for your trouble with 13.10 is the same reason for my troubles with 15.10.
Previously, I customized the boot splash for 14.10 by just editing the
splash.pcx file. That's not enough for 15.10. You actually have to put a bunch of the files in the
isolinux directory into a
cpio archive named
bootlogo. Then, put that
bootlogo file into the
For example, if you happen to have
/tmp/isolinux and it has the files from
/media/user/cdrom/isolinux, and your modified pcx files, you could do the following:
cat bootlogo | cpio -t > /tmp/list
cpio -o < /tmp/list > bootlogo
Then you can go ahead and put the contents of
/tmp/isolinux (or just the new
bootlogo) wherever you need it.
A final note, if you want to modify the splash.pcx file, be sure to put it back into a 300x300 dpi format. For example, using imagemagick:
mogrify -units PixelsPerInch -depth 300 splash.pcx
Edit: This appears to be the case for Ubuntu 16 as well. That is, applying this method you can customize the Ubuntu 16 Live CD logo.