Some hints when building with LXDE:

If you want to switch to other keyboard layout than US (in my case it is German), add these packages in the main section of "~/live-build-config/config/package-lists/kali.lists.chroot":
kbd
console-data
console-common

You should also add the packages for iceweasel and icedove there:
iceweasel
iceweasel-l10n-de
icedove
icedove-l10n-de

I suggest also add some nice stuff (those, I prefer, maybe you, too?)
wicd-gtk
lynx
bluewho
mc

And last but not least, accelerator drivers for your nice graphics card (in my case it is nvidia). Please prefer your architecture. In my case it is 32-bit (i386)
nvidia-kernel-686-pae:i386
nvidia-glx

Best results I get by cleaning old stuff, build the new stuff and burn it directly:

lb clean --purge && lb config --architecture i386 && lb build && wodim [Path-to-your-new-image]/binary.hybrid.iso

Good luck!

Hans