Hey - I've just leapt to the end of this thread, so if this has been said already, just ignore more... but the reason Atkins say no to milk (working on ketosis principles too) is because of the lactose, which knocks you out. Cream isn't as bad (I assume, as it is allowed on Atkins).
I wouldn't recommend adding anything as it becomes easy to start looking at things to cheat with, finding ways to justify things. It's not forever, you just have to do without and think about how fab you are going to look/feel when you reach your goal! Head down, and plough on!
Coffee wise, I used to add coffee to my vanilla LL shakes and make a creamy latte type thing, blasted in the microwave. Certainly fills a craving!
A x