A common customisation request is to disable the boot menu, in order to make this Web client tamper proof.

You can edit syslinux/syslinux.cfg on the USB image to look something like this:

label linux
    kernel /live/vmlinuz1
    append initrd=/live/initrd1.img boot=live quiet homepage=http://portal.webconverger.com/ nonetworking splash vga=791 username=webc hostname=webconverger union=aufs