Você pode adicionar as seguintes linhas ao seu /etc/apt/sources.list
deb http://http.kali.org/ /kali main contrib non-free
deb http://http.kali.org/ /wheezy main contrib non-free
deb http://http.kali.org/kali kali-dev main contrib non-free
deb http://http.kali.org/kali kali-dev main/debian-installer
deb-src http://http.kali.org/kali kali-dev main contrib non-free
deb http://http.kali.org/kali kali main contrib non-free
deb http://http.kali.org/kali kali main/debian-installer
deb-src http://http.kali.org/kali kali main contrib non-free
deb http://security.kali.org/kali-security kali/updates main contrib non-free
deb-src http://security.kali.org/kali-security kali/updates main contrib non-free
e, em seguida, execute
apt-get update
apt-get upgrade
apt-get install iceweasel